Actix

https://docs.rs/actix/0.13.5/actix/
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### Implementing and Starting a SyncActor

Source: https://docs.rs/actix/0.13.5/actix/sync/struct.SyncArbiter.html

Example demonstrating the implementation of a SyncActor and starting it with a SyncArbiter pool.

```rust
use actix::prelude::*;

struct Fibonacci(pub u32);


struct SyncActor;

impl Actor for SyncActor {
    // It's important to note that you use "SyncContext" here instead of "Context".
    type Context = SyncContext<Self>;
}

impl Handler<Fibonacci> for SyncActor {
    type Result = Result<u64, ()>;

    fn handle(&mut self, msg: Fibonacci, _: &mut Self::Context) -> Self::Result {
        if msg.0 == 0 {
            Err(())
        } else if msg.0 == 1 {
            Ok(1)
        } else {
            let mut i = 0;
            let mut sum = 0;
            let mut last = 0;
            let mut curr = 1;
            while i < msg.0 - 1 {
                sum = last + curr;
                last = curr;
                curr = sum;
                i += 1;
            }
            Ok(sum)
        }
    }
}

fn main() {
    System::new().block_on(async {
        // Start the SyncArbiter with 2 threads, and receive the address of the Actor pool.
        let addr = SyncArbiter::start(2, || SyncActor);

        // send 5 messages
        for n in 5..10 {
            // As there are 2 threads, there are at least 2 messages always being processed
            // concurrently by the SyncActor.
            addr.do_send(Fibonacci(n));
        }

    });
}
```

--------------------------------

### Implementing and Starting a Supervisor

Source: https://docs.rs/actix/0.13.5/actix/prelude/struct.Supervisor.html

Example showing how to implement the Supervised trait for an actor and start it using a Supervisor.

```rust
#[derive(Message)]
#[rtype(result = "()")]
struct Die;

struct MyActor;

impl Actor for MyActor {
    type Context = Context<Self>;
}

// To use actor with supervisor actor has to implement `Supervised` trait
impl actix::Supervised for MyActor {
    fn restarting(&mut self, ctx: &mut Context<MyActor>) {
        println!("restarting");
    }
}

impl Handler<Die> for MyActor {
    type Result = ();

    fn handle(&mut self, _: Die, ctx: &mut Context<MyActor>) {
        ctx.stop();
    }
}

fn main() {
    let mut sys = System::new();

    let addr = sys.block_on(async { actix::Supervisor::start(|_| MyActor) });
    addr.do_send(Die);

    sys.run();
}
```

--------------------------------

### Example Usage of actix::run

Source: https://docs.rs/actix/0.13.5/actix/fn.run.html

Demonstrates starting the system, executing an asynchronous sleep, and stopping the system.

```rust
use std::time::{Duration, Instant};\nuse actix_rt::time::sleep;\n\nfn main() {\n  actix::run(async move {\n      sleep(Duration::from_millis(100)).await;\n      actix::System::current().stop();\n  });\n}
```

--------------------------------

### fn start(self) -> Addr<Self>

Source: https://docs.rs/actix/0.13.5/actix/trait.Actor.html

Starts a new asynchronous actor and returns its address.

```APIDOC
## fn start(self) -> Addr<Self>

### Description
Starts a new asynchronous actor and returns its address. This method is available when the actor uses the default Context.

### Signature
`fn start(self) -> Addr<Self>`

### Example
```rust
use actix::prelude::*;

struct MyActor;
impl Actor for MyActor {
    type Context = Context<Self>;
}

#[actix::main]
async fn main() {
    let addr = MyActor.start();
}
```
```

--------------------------------

### Start an actor

Source: https://docs.rs/actix/0.13.5/actix/prelude/trait.Actor.html

Demonstrates how to implement the Actor trait and start an actor instance to obtain its address.

```rust
use actix::prelude::*;\n\nstruct MyActor;\nimpl Actor for MyActor {\n    type Context = Context<Self>;\n}\n\n#[actix::main]\nasync fn main() {\n    // start actor and get its address\n    let addr = MyActor.start();\n}
```

--------------------------------

### run()

Source: https://docs.rs/actix/0.13.5/actix/prelude/struct.SystemRunner.html

Starts the event loop and returns once the System is stopped.

```APIDOC
### pub fn run(self) -> Result<(), Error>

Starts the event loop and will return once System is stopped.
```

--------------------------------

### Supervisor::start

Source: https://docs.rs/actix/0.13.5/actix/prelude/struct.Supervisor.html

Starts a new supervised actor in the current tokio runtime.

```APIDOC
## pub fn start<F>(f: F) -> Addr<A>

### Description
Starts a new supervised actor in the current tokio runtime. The actor is created using the provided factory function.

### Parameters
- **f** (FnOnce(&mut A::Context) -> A) - Required - A factory function that creates the actor instance.

### Returns
- **Addr<A>** - The address of the newly created supervised actor.
```

--------------------------------

### Timeout Usage Example

Source: https://docs.rs/actix/0.13.5/actix/clock/fn.timeout.html

Demonstrates wrapping a oneshot channel receiver with a 10ms timeout.

```rust
use tokio::time::timeout;
use tokio::sync::oneshot;

use std::time::Duration;

let (tx, rx) = oneshot::channel();

// Wrap the future with a `Timeout` set to expire in 10 milliseconds.
if let Err(_) = timeout(Duration::from_millis(10), rx).await {
    println!("did not receive value within 10 ms");
}
```

--------------------------------

### Create and use an interval_at

Source: https://docs.rs/actix/0.13.5/actix/clock/fn.interval_at.html

Demonstrates initializing an interval with a start time and period, then awaiting ticks.

```rust
use tokio::time::{interval_at, Duration, Instant};

#[tokio::main]
async fn main() {
    let start = Instant::now() + Duration::from_millis(50);
    let mut interval = interval_at(start, Duration::from_millis(10));

    interval.tick().await; // ticks after 50ms
    interval.tick().await; // ticks after 10ms
    interval.tick().await; // ticks after 10ms

    // approximately 70ms have elapsed.
}
```

--------------------------------

### get_or_start_default

Source: https://docs.rs/actix/0.13.5/actix/registry/struct.Registry.html

Queries the registry for an actor of type A. If the actor is not registered, it starts a new instance and returns its address.

```APIDOC
### pub fn get_or_start_default<A: ArbiterService + Actor<Context = Context<A>>>( &self, ) -> Addr<A>

Queries the registry for an actor, returning its address. If an actor of type A is not registered, a new actor is started and its address is returned.
```

--------------------------------

### Examples of using actix_rt::spawn

Source: https://docs.rs/actix/0.13.5/actix/fn.spawn.html

Demonstrates spawning tasks that resolve successfully, panic, or are cancelled via the JoinHandle.

```rust
// task resolves successfully
assert_eq!(actix_rt::spawn(async { 1 }).await.unwrap(), 1);

// task panics
assert!(actix_rt::spawn(async {
    panic!("panic is caught at task boundary");
})
.await
.unwrap_err()
.is_panic());

// task is cancelled before completion
let handle = actix_rt::spawn(actix_rt::time::sleep(Duration::from_secs(100)));
handle.abort();
assert!(handle.await.unwrap_err().is_cancelled());
```

--------------------------------

### Actor Initialization Methods

Source: https://docs.rs/actix/0.13.5/actix/prelude/trait.Actor.html

Static methods used to construct and start actors within the Actix system.

```APIDOC
## fn start(self) -> Addr<Self>

### Description
Starts a new asynchronous actor and returns its address.

## fn start_default() -> Addr<Self>

### Description
Constructs a new actor using the `Default` trait and starts it, returning its address.

## fn create<F>(f: F) -> Addr<Self>

### Description
Starts a new asynchronous actor using a closure that provides the `Context` object during initialization.
```

--------------------------------

### SyncArbiter::start_with_thread_builder

Source: https://docs.rs/actix/0.13.5/actix/sync/struct.SyncArbiter.html

Starts a new SyncArbiter with custom thread configuration using a thread builder factory.

```APIDOC
## SyncArbiter::start_with_thread_builder<F, BF>(threads: usize, thread_builder_factory: BF, factory: F) -> Addr<A>

### Description
Starts a new `SyncArbiter` with a specified number of worker threads. Each worker thread is configured using a `std::thread::Builder` provided by the `thread_builder_factory`.

### Parameters
- **threads** (usize) - Required - The number of worker threads to spawn.
- **thread_builder_factory** (BF) - Required - A closure that returns a `std::thread::Builder` for each thread.
- **factory** (F) - Required - A closure that returns an instance of the actor (A).
```

--------------------------------

### fn create<F>(f: F) -> Addr<Self>

Source: https://docs.rs/actix/0.13.5/actix/trait.Actor.html

Starts a new asynchronous actor using a factory function that provides access to the actor's context.

```APIDOC
## fn create<F>(f: F) -> Addr<Self>

### Description
Starts a new asynchronous actor given a factory function. Use this method if you need the Context object during actor initialization.

### Signature
`fn create<F>(f: F) -> Addr<Self> where Self: Actor<Context = Context<Self>>, F: FnOnce(&mut Context<Self>) -> Self`

### Example
```rust
use actix::prelude::*;

struct MyActor {
    val: usize,
}
impl Actor for MyActor {
    type Context = Context<Self>;
}

#[actix::main]
async fn main() {
    let addr = MyActor::create(|ctx: &mut Context<MyActor>| MyActor { val: 10 });
}
```
```

--------------------------------

### Implement Actor with SyncContext

Source: https://docs.rs/actix/0.13.5/actix/sync/struct.SyncContext.html

Example of using SyncContext as the actor context type.

```rust
use actix::prelude::*;



struct SyncActor;

impl Actor for SyncActor {
    // It's important to note that you use "SyncContext" here instead of "Context".
    type Context = SyncContext<Self>;
}
```

--------------------------------

### Start a supervised actor

Source: https://docs.rs/actix/0.13.5/actix/prelude/struct.Supervisor.html

Initializes a new supervised actor in the current tokio runtime. The returned address type can be explicitly defined.

```rust
struct MyActor;

impl Actor for MyActor {
    type Context = Context<Self>;
}

// Get `Addr` of a MyActor actor
let addr = actix::Supervisor::start(|_| MyActor);
```

--------------------------------

### Implementing StreamHandler for an Actor

Source: https://docs.rs/actix/0.13.5/actix/prelude/trait.StreamHandler.html

Example showing how to implement StreamHandler to process stream items and handle completion.

```rust
use actix::prelude::*;
use futures_util::stream::once;

#[derive(Message)]
#[rtype(result = "()")]
struct Ping;

struct MyActor;

impl StreamHandler<Ping> for MyActor {
    fn handle(&mut self, item: Ping, ctx: &mut Context<MyActor>) {
        println!("PING");
        System::current().stop()
    }

    fn finished(&mut self, ctx: &mut Self::Context) {
        println!("finished");
    }
}

impl Actor for MyActor {
   type Context = Context<Self>;

   fn started(&mut self, ctx: &mut Context<Self>) {
       Self::add_stream(once(async { Ping }), ctx);
   }
}

#[actix::main]
async fn main() {
    MyActor.start();
}
```

--------------------------------

### SyncArbiter::start

Source: https://docs.rs/actix/0.13.5/actix/sync/struct.SyncArbiter.html

Starts a new SyncArbiter with a specified number of worker threads and an actor factory.

```APIDOC
## SyncArbiter::start<F>(threads: usize, factory: F) -> Addr<A>

### Description
Starts a new `SyncArbiter` with a specified number of worker threads. Returns a single address of the started actor, which is used to communicate with the actors handled by the arbiter.

### Parameters
- **threads** (usize) - Required - The number of worker threads to spawn.
- **factory** (F) - Required - A closure that returns an instance of the actor (A).
```

--------------------------------

### SyncArbiter::start

Source: https://docs.rs/actix/0.13.5/actix/sync/struct.SyncArbiter.html

Starts a SyncArbiter with a specified number of threads and an actor factory, returning an address to the actor pool.

```APIDOC
## SyncArbiter::start

### Description
Starts the SyncArbiter with a defined number of threads and an actor factory. It returns an address that can be used to send messages to the pool of hosted Sync Actors.

### Signature
`pub fn start<F, A>(num: usize, factory: F) -> Addr<A>`

### Parameters
- **num** (usize) - The number of threads to spawn for the actor pool.
- **factory** (F) - A closure or function that returns an instance of the Actor (A).

### Returns
- **Addr<A>** - An address to the pool of Sync Actors.
```

--------------------------------

### SystemRegistry::get<A>

Source: https://docs.rs/actix/0.13.5/actix/registry/struct.SystemRegistry.html

Retrieves the address of a system service. If the service actor is not currently running, it will be started automatically.

```APIDOC
## pub fn get<A: SystemService + Actor<Context = Context<A>>>(&mut self) -> Addr<A>

### Description
Returns the address of the specified service. If the service actor is not running, it gets started in the system.

### Parameters
- **A** (Generic Type) - The actor type that implements `SystemService` and `Actor`.
```

--------------------------------

### IntervalFunc::new_at

Source: https://docs.rs/actix/0.13.5/actix/utils/struct.IntervalFunc.html

Constructs a new IntervalFunc that starts at a specific time and then executes at a specified interval.

```APIDOC
## pub fn new_at<F>(start: Instant, interval: Duration, task: F) -> IntervalFunc<A>

### Description
Constructs an `IntervalFunc` using the given `start` time, `interval` duration, and `task` function.

### Parameters
- **start** (Instant) - The time at which the first execution should occur.
- **interval** (Duration) - The time duration between subsequent executions.
- **task** (F) - A closure with signature `FnMut(&mut A, &mut A::Context) + 'static` to be executed.
```

--------------------------------

### Implement Handler with ResponseActFuture

Source: https://docs.rs/actix/0.13.5/actix/prelude/type.ResponseActFuture.html

Example demonstrating how to return a ResponseActFuture from an actor's message handler to perform async operations.

```rust
use actix::prelude::*;

#[derive(Message)]
#[rtype(result = "Result<usize, ()>")]
struct Msg;

struct MyActor;

impl Actor for MyActor {
    type Context = Context<Self>;
}

impl Handler<Msg> for MyActor {
    type Result = ResponseActFuture<Self, Result<usize, ()>>;

    fn handle(&mut self, _: Msg, _: &mut Context<Self>) -> Self::Result {
        Box::pin(
            async {
                // Some async computation
                42
            }
            .into_actor(self) // converts future to ActorFuture
            .map(|res, _act, _ctx| {
                // Do some computation with actor's state or context
                Ok(res)
            }),
        )
    }
}
```

--------------------------------

### Supervisor::start

Source: https://docs.rs/actix/0.13.5/actix/prelude/struct.Supervisor.html

Starts a new actor under the management of a supervisor. The supervisor will monitor the actor and trigger the restarting method if the actor fails.

```APIDOC
## Supervisor::start

### Description
Starts a new actor under the management of a supervisor. The supervisor will monitor the actor and trigger the restarting method if the actor fails.

### Signature
`pub fn start<F, A>(f: F) -> Addr<A> where F: FnOnce(&mut Context<A>) -> A + Send, A: Supervised + Actor<Context = Context<A>>`

### Parameters
- **f** (FnOnce) - Required - A closure that creates the actor instance.

### Returns
- **Addr<A>** - The address of the supervised actor.
```

--------------------------------

### Implement MessageResponse for ResponseFuture

Source: https://docs.rs/actix/0.13.5/actix/prelude/type.ResponseFuture.html

Examples demonstrating how to handle different message result types using ResponseFuture within an Actix actor handler.

```rust
pub struct MyQuestion{}
impl Message for MyQuestion {
    type Result = Result<u8,u8>;
}
impl Handler<MyQuestion> for MyActorAsync {
    type Result = ResponseFuture<Result<u8,u8>>;
    fn handle(&mut self, question: MyQuestion, _ctx: &mut Context<Self>) -> Self::Result {
        Box::pin(async {Ok(5)})
    }
}
```

```rust
pub struct MyQuestion{}
impl Message for MyQuestion {
    type Result = Option<u8>;
}
impl Handler<MyQuestion> for MyActorAsync {
    type Result = ResponseFuture<Option<u8>>;
    fn handle(&mut self, question: MyQuestion, _ctx: &mut Context<Self>) -> Self::Result {
        Box::pin(async {Some(5)})
    }
}
```

```rust
pub struct MyQuestion{}
impl Message for MyQuestion {
    type Result = u8;
}
impl Handler<MyQuestion> for MyActorAsync {
    type Result = ResponseFuture<u8>;
    fn handle(&mut self, question: MyQuestion, _ctx: &mut Context<Self>) -> Self::Result {
        Box::pin(async {5})
    }
}
```

--------------------------------

### Supervisor::start_in_arbiter

Source: https://docs.rs/actix/0.13.5/actix/prelude/struct.Supervisor.html

Starts a new supervised actor in a specific arbiter's thread.

```APIDOC
## pub fn start_in_arbiter<F>(sys: &ArbiterHandle, f: F) -> Addr<A>

### Description
Starts a new supervised actor within the thread managed by the specified ArbiterHandle.

### Parameters
- **sys** (&ArbiterHandle) - Required - The handle to the arbiter where the actor will run.
- **f** (FnOnce(&mut Context<A>) -> A) - Required - A factory function that creates the actor instance.

### Returns
- **Addr<A>** - The address of the newly created supervised actor.
```

--------------------------------

### Mocker Handler Implementation

Source: https://docs.rs/actix/0.13.5/actix/prelude/trait.Handler.html

Example implementation of the Handler trait for the Mocker struct.

```rust
impl<M, T: Sized + Unpin + 'static> Handler<M> for Mocker<T>
where M: Message + 'static, <M as Message>::Result: MessageResponse<Mocker<T>, M>,
Source§
#### type Result = <M as Message>::Result
```

--------------------------------

### Implementing ActorFuture in a Handler

Source: https://docs.rs/actix/0.13.5/actix/fut/future/trait.ActorFuture.html

Example of using ActorFuture to defer work to another actor and update the initiating actor's state upon completion.

```rust
use actix::prelude::*;

// The response type returned by the actor future
type OriginalActorResponse = ();
// The error type returned by the actor future
type MessageError = ();
// This is the needed result for the DeferredWork message
// It's a result that combine both Response and Error from the future response.
type DeferredWorkResult = Result<OriginalActorResponse, MessageError>;

impl Handler<DeferredWork> for OriginalActor {
    // Notice the `Response` is an `ActorFuture`-ized version of `Self::Message::Result`.
    type Result = ResponseActFuture<Self, DeferredWorkResult>;

    fn handle(&mut self, _msg: DeferredWork, _ctx: &mut Context<Self>) -> Self::Result {
        // this creates a `Future` representing the `.send` and subsequent
        // `Result` from `other_actor`
        let update_self = self.other_actor
            .send(OtherMessage {})
            // Wrap that future so chained handlers can access the actor
            // (`self` in the synchronous code) as well as the context.
            .into_actor(self)
            // once the wrapped future resolves, update this actor's state
            .map(|result, actor, _ctx| {
                match result {
                    Ok(v) => {
                        // update actor (self) state
                        actor.inner_state.update_from(v);
                        Ok(())
                    },
                    // Failed to send message to other_actor
                    Err(_e) => Err(()),
                }
            });

        // box and return the wrapped future
        Box::pin(update_self)
    }
}
```

--------------------------------

### Arbiter::new

Source: https://docs.rs/actix/0.13.5/actix/prelude/struct.Arbiter.html

Spawns a new Arbiter thread and starts its event loop. Panics if a System is not registered on the current thread.

```APIDOC
## pub fn new() -> Arbiter

### Description
Spawn a new Arbiter thread and start its event loop.

### Panics
Panics if a System is not registered on the current thread.
```

--------------------------------

### Using TimerFunc in an Actor

Source: https://docs.rs/actix/0.13.5/actix/utils/struct.TimerFunc.html

Example of spawning a delayed function into an actor's context using TimerFunc.

```rust
use std::time::Duration;
use actix::prelude::*;
use actix::utils::TimerFunc;

struct MyActor;

impl MyActor {
    fn stop(&mut self, context: &mut Context<Self>) {
        System::current().stop();
    }
}

impl Actor for MyActor {
   type Context = Context<Self>;

   fn started(&mut self, context: &mut Context<Self>) {
       // spawn a delayed future into our context
       TimerFunc::new(Duration::from_millis(100), Self::stop)
           .spawn(context);
   }
}
```

--------------------------------

### actix::run<R>(f: R) -> Result<()>

Source: https://docs.rs/actix/0.13.5/actix/fn.run.html

Starts the actix system and executes the supplied future. The function blocks the current thread until the system shuts down via System::current().stop().

```APIDOC
## fn run<R>(f: R) -> Result<()>

### Description
Starts the actix system and executes the supplied future. This function creates and starts the system with default configuration, spawns the future onto the current arbiter, and blocks the current thread until the system shuts down.

### Signature
`pub fn run<R>(f: R) -> Result<()> where R: Future<Output = ()> + 'static`

### Parameters
- **f** (R) - Required - A future that implements `Future<Output = ()> + 'static` to be executed by the system.

### Panics
This function will panic if the actix system is already running.

### Example
```rust
use std::time::{Duration, Instant};
use actix_rt::time::sleep;

fn main() {
  actix::run(async move {
      sleep(Duration::from_millis(100)).await;
      actix::System::current().stop();
  });
}
```
```

--------------------------------

### Create a failed future with actix::fut::err

Source: https://docs.rs/actix/0.13.5/actix/fut/future/result/fn.err.html

Initializes a future that resolves immediately to an error result. Requires the actix crate and appropriate actor context setup.

```rust
pub fn err<T, E>(e: E) -> Ready<Result<T, E>> ⓘ
```

```rust
use actix::{fut, Actor, Context};

struct MyActor;
impl Actor for MyActor {
    type Context = Context<Self>;
}

let future_of_err_1 = fut::err::<u32, u32>(1);
```

--------------------------------

### Using SystemRegistry with SystemService

Source: https://docs.rs/actix/0.13.5/actix/registry/struct.SystemRegistry.html

Demonstrates how to implement SystemService and interact with it using the registry.

```rust
use actix::prelude::*;\n\n#[derive(Message)]\n#[rtype(result = "()")]\nstruct Ping;\n\n#[derive(Default)]\nstruct MyActor1;\n\nimpl Actor for MyActor1 {\n    type Context = Context<Self>;\n}\nimpl actix::Supervised for MyActor1 {}\n\nimpl SystemService for MyActor1 {\n    fn service_started(&mut self, ctx: &mut Context<Self>) {\n        println!("Service started");\n    }\n}\n\nimpl Handler<Ping> for MyActor1 {\n    type Result = ();\n\n    fn handle(&mut self, _: Ping, ctx: &mut Context<Self>) {\n        println!("ping");\n    }\n}\n\nstruct MyActor2;\n\nimpl Actor for MyActor2 {\n    type Context = Context<Self>;\n\n    fn started(&mut self, _: &mut Context<Self>) {\n        let act = MyActor1::from_registry();\n        act.do_send(Ping);\n    }\n}\n\n#[actix::main]\nasync fn main() {\n    // Start MyActor2\n    let addr = MyActor2.start();\n}
```

--------------------------------

### System::new

Source: https://docs.rs/actix/0.13.5/actix/prelude/struct.System.html

Creates a new system. Panics if the underlying Tokio runtime cannot be created.

```APIDOC
### pub fn new() -> SystemRunner

Creates a new system. Panics if the underlying Tokio runtime can not be created.
```

--------------------------------

### interval_at(start: Instant, period: Duration) -> Interval

Source: https://docs.rs/actix/0.13.5/actix/clock/fn.interval_at.html

Creates a new Interval that yields with an interval of period with the first tick completing at start. The default MissedTickBehavior is Burst, which can be configured via set_missed_tick_behavior.

```APIDOC
## interval_at(start: Instant, period: Duration) -> Interval

### Description
Creates a new `Interval` that yields with an interval of `period` with the first tick completing at `start`. The interval ticks indefinitely until the `Interval` value is dropped.

### Parameters
- **start** (Instant) - The time at which the first tick completes.
- **period** (Duration) - The duration between subsequent ticks.

### Panics
This function panics if `period` is zero.

### Example
```rust
use tokio::time::{interval_at, Duration, Instant};

#[tokio::main]
async fn main() {
    let start = Instant::now() + Duration::from_millis(50);
    let mut interval = interval_at(start, Duration::from_millis(10));

    interval.tick().await; // ticks after 50ms
    interval.tick().await; // ticks after 10ms
    interval.tick().await; // ticks after 10ms
}
```
```

--------------------------------

### as_mut

Source: https://docs.rs/actix/0.13.5/actix/prelude/type.ResponseFuture.html

Gets a mutable reference to the pinned value this Pin points to.

```APIDOC
## pub fn as_mut(&mut self) -> Pin<&mut <Ptr as Deref>::Target>

### Description
Gets a mutable reference to the pinned value this Pin<Ptr> points to. This is useful when doing multiple calls to functions that consume the pinning pointer.
```

--------------------------------

### #[main]

Source: https://docs.rs/actix/0.13.5/actix/attr.main.html

Marks an async main function as the actix system entry-point.

```APIDOC
## #[main]

### Description
Marks an async main function as the `actix` system entry-point. This macro is available only when the `macros` feature flag is enabled.

### Usage
```rust
#[actix::main]
async fn main() {
    println!("Hello world");
}
```
```

--------------------------------

### as_ref

Source: https://docs.rs/actix/0.13.5/actix/prelude/type.ResponseFuture.html

Gets a shared reference to the pinned value this Pin points to.

```APIDOC
## pub fn as_ref(&self) -> Pin<&<Ptr as Deref>::Target>

### Description
Gets a shared reference to the pinned value this Pin points to. This is a safe way to go from &Pin<Pointer<T>> to Pin<&T>.
```

--------------------------------

### Create an actor with context

Source: https://docs.rs/actix/0.13.5/actix/prelude/trait.Actor.html

Shows how to initialize an actor using the create method, which provides access to the actor's context during construction.

```rust
use actix::prelude::*;\n\nstruct MyActor {\n    val: usize,\n}\nimpl Actor for MyActor {\n    type Context = Context<Self>;\n}\n\n#[actix::main]\nasync fn main() {\n    let addr = MyActor::create(|ctx: &mut Context<MyActor>| MyActor { val: 10 });\n}
```

--------------------------------

### System::with_tokio_rt

Source: https://docs.rs/actix/0.13.5/actix/prelude/struct.System.html

Creates a new System using the Tokio Runtime returned from a closure.

```APIDOC
### pub fn with_tokio_rt<F>(runtime_factory: F) -> SystemRunner
where F: FnOnce() -> Runtime

Create a new System using the Tokio Runtime returned from a closure.
```

--------------------------------

### as_deref_mut

Source: https://docs.rs/actix/0.13.5/actix/prelude/type.ResponseFuture.html

Gets Pin<&mut T> to the underlying pinned value from this nested Pin-pointer.

```APIDOC
## pub fn as_deref_mut(self: Pin<&mut Pin<Ptr>>) -> Pin<&mut <Ptr as Deref>::Target>

### Description
Gets Pin<&mut T> to the underlying pinned value from this nested Pin-pointer.
```

--------------------------------

### Arbiter::try_current

Source: https://docs.rs/actix/0.13.5/actix/struct.Arbiter.html

Attempts to get the current running arbiter handle without panicking.

```APIDOC
## pub fn try_current() -> Option<ArbiterHandle>

### Description
Try to get current running arbiter handle. Returns None if no Arbiter has been started.
```

--------------------------------

### Create and run a new Context

Source: https://docs.rs/actix/0.13.5/actix/prelude/struct.Context.html

Demonstrates creating a context without spawning it and then running an actor within it.

```rust
struct Actor1 {
    actor2_addr: Addr<Actor2>,
}

struct Actor2 {
    actor1_addr: Addr<Actor1>,
}

let ctx1 = Context::<Actor1>::new();
let ctx2 = Context::<Actor2>::new();

let actor1 = Actor1 { actor2_addr: ctx2.address() };
let actor2 = Actor2 { actor1_addr: ctx1.address() };

ctx1.run(actor1);
ctx2.run(actor2);
```

--------------------------------

### System::current

Source: https://docs.rs/actix/0.13.5/actix/prelude/struct.System.html

Retrieves the currently running system. Panics if no system is registered on the current thread.

```APIDOC
### pub fn current() -> System

Get current running system. Panics if no system is registered on the current thread.
```

--------------------------------

### Set mailbox capacity

Source: https://docs.rs/actix/0.13.5/actix/prelude/struct.Context.html

Configures the mailbox capacity for an actor within its started lifecycle method.

```rust
struct MyActor;
impl Actor for MyActor {
    type Context = Context<Self>;

    fn started(&mut self, ctx: &mut Self::Context) {
        ctx.set_mailbox_capacity(1);
        System::current().stop();
    }
}

let addr = sys.block_on(async { MyActor.start() });
sys.run();
```

--------------------------------

### Implement MessageResult in an Actor

Source: https://docs.rs/actix/0.13.5/actix/prelude/struct.MessageResult.html

Example showing how to use MessageResult as the return type for a message handler.

```rust
use actix::prelude::*;

#[derive(Message)]
#[rtype(Response)]
struct Msg;

struct Response;

struct MyActor;

impl Actor for MyActor {
    type Context = Context<Self>;
}

impl Handler<Msg> for MyActor {
    type Result = MessageResult<Msg>;

    fn handle(&mut self, _: Msg, _: &mut Context<Self>) -> Self::Result {
        MessageResult(Response {})
    }
}
```

--------------------------------

### Create Response instances

Source: https://docs.rs/actix/0.13.5/actix/prelude/struct.Response.html

Methods for creating asynchronous and synchronous responses.

```rust
pub fn fut<T>(fut: T) -> Self
where T: Future<Output = I> + 'static,
```

```rust
pub fn reply(val: I) -> Self
```

--------------------------------

### Writer::handle

Source: https://docs.rs/actix/0.13.5/actix/io/struct.Writer.html

Returns the SpawnHandle for this writer.

```APIDOC
### pub fn handle(&self) -> SpawnHandle

Returns the SpawnHandle associated with the writer.
```

--------------------------------

### Basic usage of interval

Source: https://docs.rs/actix/0.13.5/actix/clock/fn.interval.html

Demonstrates creating an interval and awaiting ticks, where the first tick completes immediately.

```rust
use tokio::time::{self, Duration};

#[tokio::main]
async fn main() {
    let mut interval = time::interval(Duration::from_millis(10));

    interval.tick().await; // ticks immediately
    interval.tick().await; // ticks after 10ms
    interval.tick().await; // ticks after 10ms

    // approximately 20ms have elapsed.
}
```

--------------------------------

### Create an Instant

Source: https://docs.rs/actix/0.13.5/actix/clock/struct.Instant.html

Obtain the current time as an Instant.

```rust
use tokio::time::Instant;

let now = Instant::now();
```

--------------------------------

### System::try_current

Source: https://docs.rs/actix/0.13.5/actix/prelude/struct.System.html

Attempts to retrieve the currently running system without panicking.

```APIDOC
### pub fn try_current() -> Option<System>

Try to get current running system. Returns None if no System has been started.
```

--------------------------------

### Context::run

Source: https://docs.rs/actix/0.13.5/actix/struct.Context.html

Spawns an actor into the context and returns its address.

```APIDOC
## pub fn run(self, act: A) -> Addr<A>

### Description
Spawns the provided actor into the context and returns an address to communicate with it.
```

--------------------------------

### Define Actix main entry-point

Source: https://docs.rs/actix/0.13.5/actix/attr.main.html

Marks an async main function as the Actix system entry-point. Requires the macros feature flag.

```rust
#[main]
```

```rust
#[actix::main]
async fn main() {
    println!("Hello world");
}
```

--------------------------------

### #[actix::test]

Source: https://docs.rs/actix/0.13.5/actix/attr.test.html

Marks an async test function to use the actix system entry-point. This macro is available when the 'macros' feature flag is enabled.

```APIDOC
## #[actix::test]

### Description
Marks async test functions to use the `actix` system entry-point. This macro is required for testing asynchronous code within the Actix framework.

### Usage
Apply the attribute to an `async fn` test function.

### Example
```rust
#[actix::test]
async fn my_test() {
    assert!(true);
}
```
```

--------------------------------

### Handle Message with Option

Source: https://docs.rs/actix/0.13.5/actix/dev/trait.MessageResponse.html

Demonstrates implementing a handler that returns an Option using ResponseFuture.

```rust
pub struct MyQuestion{}
impl Message for MyQuestion {
    type Result = Option<u8>;
}
impl Handler<MyQuestion> for MyActorAsync {
    type Result = ResponseFuture<Option<u8>>;
    fn handle(&mut self, question: MyQuestion, _ctx: &mut Context<Self>) -> Self::Result {
        Box::pin(async {Some(5)})
    }
}
```

--------------------------------

### Implementing AtomicResponse in a Handler

Source: https://docs.rs/actix/0.13.5/actix/prelude/struct.AtomicResponse.html

Example of using AtomicResponse within a Handler to ensure exclusive state access during asynchronous operations.

```rust
impl Handler<Msg> for MyActor {
    type Result = AtomicResponse<Self, usize>;

    fn handle(&mut self, _: Msg, _: &mut Context<Self>) -> Self::Result {
        AtomicResponse::new(Box::pin(
            async {}
                .into_actor(self)
                .map(|_, this, _| {
                    this.0 = 30;
                })
                .then(|_, this, _| {
                    sleep(Duration::from_secs(3)).into_actor(this)
                })
                .map(|_, this, _| {
                    this.0 -= 1;
                    this.0
                }),
        ))
    }
}
```

--------------------------------

### Writer::new

Source: https://docs.rs/actix/0.13.5/actix/io/struct.Writer.html

Creates a new instance of the Writer.

```APIDOC
### pub fn new<A, C>(io: T, ctx: &mut C) -> Self

Creates a new Writer instance wrapping an AsyncWrite type.
```

--------------------------------

### Actor Trait Definition

Source: https://docs.rs/actix/0.13.5/actix/prelude/trait.Actor.html

The Actor trait requires implementation of an ActorContext and provides default lifecycle hooks and methods for starting actors.

```rust
pub trait Actor:
    Sized
    + Unpin
    + 'static {
    type Context: ActorContext;

    // Provided methods
    fn started(&mut self, ctx: &mut Self::Context) { ... }
    fn stopping(&mut self, ctx: &mut Self::Context) -> Running { ... }
    fn stopped(&mut self, ctx: &mut Self::Context) { ... }
    fn start(self) -> Addr<Self>
       where Self: Actor<Context = Context<Self>> { ... }
    fn start_default() -> Addr<Self>
       where Self: Actor<Context = Context<Self>> + Default { ... }
    fn start_in_arbiter<F>(wrk: &ArbiterHandle, f: F) -> Addr<Self>
       where Self: Actor<Context = Context<Self>>,
             F: FnOnce(&mut Context<Self>) -> Self + Send + 'static { ... }
    fn create<F>(f: F) -> Addr<Self>
       where Self: Actor<Context = Context<Self>>,
             F: FnOnce(&mut Context<Self>) -> Self { ... }
}
```

--------------------------------

### Import Actix Dev Prelude

Source: https://docs.rs/actix/0.13.5/actix/dev/index.html

Use this glob import to bring common Actix traits into scope for library development.

```rust
use actix::dev::*;
```

--------------------------------

### ready<T>(t: T) -> Ready<T>

Source: https://docs.rs/actix/0.13.5/actix/fut/fn.ready.html

Creates a future that is immediately ready with a value.

```APIDOC
## ready<T>(t: T) -> Ready<T>

### Description
Creates a future that is immediately ready with a value.

### Signature
`pub fn ready<T>(t: T) -> Ready<T>`

### Example
```rust
use futures::future;

let a = future::ready(1);
assert_eq!(a.await, 1);
```
```

--------------------------------

### Importing the Actix Prelude

Source: https://docs.rs/actix/0.13.5/actix/prelude/index.html

Use this glob import at the top of modules to access common Actix traits and types.

```rust
use actix::prelude::*;
```

--------------------------------

### pub fn upgrade(&self) -> Option<Addr<A>>

Source: https://docs.rs/actix/0.13.5/actix/struct.WeakAddr.html

Attempts to upgrade the WeakAddr pointer to an Addr. Returns None if the actor has been dropped or the address is disconnected.

```APIDOC
## pub fn upgrade(&self) -> Option<Addr<A>>

### Description
Attempts to upgrade the `WeakAddr<A>` pointer to an `Addr<A>`. Returns `None` if the actor has since been dropped or the underlying address is disconnected.
```

--------------------------------

### fn spawn<Fut>(f: Fut) -> JoinHandle<<Fut as Future>::Output>

Source: https://docs.rs/actix/0.13.5/actix/fn.spawn.html

Spawns a future on the current thread as a new task. The task can be cancelled via the returned JoinHandle, and panics within the future are caught.

```APIDOC
## fn spawn<Fut>(f: Fut) -> JoinHandle<<Fut as Future>::Output>

### Description
Spawns a future on the current thread as a new task. If not immediately awaited, the task can be cancelled using `JoinHandle::abort`. The provided future is spawned as a new task; therefore, panics are caught.

### Signature
`pub fn spawn<Fut>(f: Fut) -> JoinHandle<<Fut as Future>::Output>`

### Constraints
- `Fut`: Future + 'static
- `<Fut as Future>::Output`: 'static

### Panics
Panics if the Actix system is not running.

### Example
```rust
// task resolves successfully
assert_eq!(actix_rt::spawn(async { 1 }).await.unwrap(), 1);

// task panics
assert!(actix_rt::spawn(async {
    panic!("panic is caught at task boundary");
})
.await
.unwrap_err()
.is_panic());

// task is cancelled before completion
let handle = actix_rt::spawn(actix_rt::time::sleep(Duration::from_secs(100)));
handle.abort();
assert!(handle.await.unwrap_err().is_cancelled());
```
```

--------------------------------

### ok(t: T) -> Ready<Result<T, E>>

Source: https://docs.rs/actix/0.13.5/actix/fut/future/result/index.html

Creates a leaf future from an immediate value of a finished and successful computation.

```APIDOC
## ok(t: T)

### Description
Creates a "leaf future" from an immediate value of a finished and successful computation.

### Parameters
- **t** (T) - Required - The success value to be returned by the future.
```

--------------------------------

### Demonstrate unsafe pinning with Rc

Source: https://docs.rs/actix/0.13.5/actix/fut/future/type.LocalBoxActorFuture.html

Illustrates how creating a Pin from an Rc can lead to undefined behavior due to potential aliasing and mutable access after dropping the pin.

```rust
use std::rc::Rc;
use std::pin::Pin;

fn move_pinned_rc<T>(mut x: Rc<T>) {
    // This should mean the pointee can never move again.
    let pin = unsafe { Pin::new_unchecked(Rc::clone(&x)) };
    {
        let p: Pin<&T> = pin.as_ref();
        // ...
    }
    drop(pin);

    let content = Rc::get_mut(&mut x).unwrap(); // Potential UB down the road ⚠️
    // Now, if `x` was the only reference, we have a mutable reference to
    // data that we pinned above, which we could use to move it as we have
    // seen in the previous example. We have violated the pinning API contract.
}
```

--------------------------------

### Envelope Constructor Methods

Source: https://docs.rs/actix/0.13.5/actix/dev/struct.Envelope.html

Methods for creating new Envelope instances, including standard message creation and proxy-based creation.

```rust
pub fn new<M>(msg: M, tx: Option<Sender<M::Result>>) -> Self
where A: Handler<M>, A::Context: AsyncContext<A>, M: Message + Send + 'static, M::Result: Send,
```

```rust
pub fn with_proxy(proxy: Box<dyn EnvelopeProxy<A> + Send>) -> Self
```

--------------------------------

### Safely pin closures using the pin! macro

Source: https://docs.rs/actix/0.13.5/actix/fut/future/type.LocalBoxActorFuture.html

Shows the recommended approach for pinning futures within closures by using the pin! macro to avoid unsafe pinning.

```rust
use std::pin::pin;
use std::task::Context;
use std::future::Future;

fn move_pinned_closure(mut x: impl Future, cx: &mut Context<'_>) {
    let mut x = pin!(x);
    // Create a closure that captures `x: Pin<&mut _>`, which is safe to move.
    let mut closure = move || {
        let _ignore = x.as_mut().poll(cx);
    };
    // Call the closure, so the future can assume it has been pinned.
    closure();
    // Move the closure somewhere else.
    let mut moved = closure;
    // Calling it again here is fine (except that we might be polled a future that already
    // returned `Poll::Ready`, but that is a separate problem).
    moved();
}
```

--------------------------------

### SystemRegistry::set<A>

Source: https://docs.rs/actix/0.13.5/actix/registry/struct.SystemRegistry.html

Registers a new actor in the system registry using its address.

```APIDOC
## pub fn set<A: SystemService + Actor<Context = Context<A>>>(addr: Addr<A>)

### Description
Adds a new actor to the registry by its address. This method will panic if the actor is already running.

### Parameters
- **addr** (Addr<A>) - The address of the actor to register.
```

--------------------------------

### Define and use an ArbiterService

Source: https://docs.rs/actix/0.13.5/actix/registry/struct.Registry.html

Demonstrates defining an actor as an ArbiterService and accessing it from the registry within a separate Arbiter.

```rust
use actix::prelude::*;

#[derive(Message)]
#[rtype(result = "()")]
struct Ping;

#[derive(Default)]
struct MyActor1;

impl Actor for MyActor1 {
    type Context = Context<Self>;
}
impl actix::Supervised for MyActor1 {}

impl ArbiterService for MyActor1 {
   fn service_started(&mut self, ctx: &mut Context<Self>) {
      println!("Service started");
   }
}

impl Handler<Ping> for MyActor1 {
   type Result = ();

   fn handle(&mut self, _: Ping, ctx: &mut Context<Self>) {
      println!("ping");
   }
}

struct MyActor2;

impl Actor for MyActor2 {
   type Context = Context<Self>;

   fn started(&mut self, _: &mut Context<Self>) {
      // get MyActor1 address from the registry
      let act = MyActor1::from_registry();
      act.do_send(Ping);
   }
}

#[actix::main]
async fn main() {
    // Start MyActor2 in new Arbiter
    Arbiter::new().spawn_fn(|| {
        MyActor2.start();
    });
}
```

--------------------------------

### Construct Pin with Unpin type

Source: https://docs.rs/actix/0.13.5/actix/fut/future/type.LocalBoxActorFuture.html

Demonstrates creating a Pin for a type that implements Unpin.

```rust
use std::pin::Pin;

let mut val: u8 = 5;

// Since `val` doesn't care about being moved, we can safely create a "facade" `Pin`
// which will allow `val` to participate in `Pin`-bound apis  without checking that
// pinning guarantees are actually upheld.
let mut pinned: Pin<&mut u8> = Pin::new(&mut val);
```

--------------------------------

### Demonstrate unsafe pinning with mutable references

Source: https://docs.rs/actix/0.13.5/actix/fut/future/type.LocalBoxActorFuture.html

Illustrates how creating a Pin from a mutable reference can lead to undefined behavior if the value is moved after pinning.

```rust
use std::mem;
use std::pin::Pin;

fn move_pinned_ref<T>(mut a: T, mut b: T) {
    unsafe {
        let p: Pin<&mut T> = Pin::new_unchecked(&mut a);
        // This should mean the pointee `a` can never move again.
    }
    mem::swap(&mut a, &mut b); // Potential UB down the road ⚠️
    // The address of `a` changed to `b`'s stack slot, so `a` got moved even
    // though we have previously pinned it! We have violated the pinning API contract.
}
```

--------------------------------

### Use with select!

Source: https://docs.rs/actix/0.13.5/actix/clock/struct.Sleep.html

Demonstrates pinning a Sleep instance to use it within a select! loop.

```rust
use tokio::time::{self, Duration, Instant};

#[tokio::main]
async fn main() {
    let sleep = time::sleep(Duration::from_millis(10));
    tokio::pin!(sleep);

    loop {
        tokio::select! {
            () = &mut sleep => {
                println!("timer elapsed");
                sleep.as_mut().reset(Instant::now() + Duration::from_millis(50));
            },
        }
    }
}
```

--------------------------------

### Registering a stream with add_stream

Source: https://docs.rs/actix/0.13.5/actix/prelude/trait.AsyncContext.html

Demonstrates how to register a stream with an actor's context using add_stream, allowing the actor to process stream items as messages.

```rust
use actix::prelude::*;
use futures_util::stream::once;

#[derive(Message)]
#[rtype(result = "()")]
struct Ping;

struct MyActor;

impl StreamHandler<Ping> for MyActor {

    fn handle(&mut self, item: Ping, ctx: &mut Context<MyActor>) {
        println!("PING");
        System::current().stop();
    }

    fn finished(&mut self, ctx: &mut Self::Context) {
        println!("finished");
    }
}

impl Actor for MyActor {
   type Context = Context<Self>;

   fn started(&mut self, ctx: &mut Context<Self>) {
       // add stream
       ctx.add_stream(once(async { Ping }));
   }
}

fn main() {
    let mut sys = System::new();
    let addr = sys.block_on(async { MyActor.start() });
    sys.run();
 }
```

--------------------------------

### Addr<A>::downgrade

Source: https://docs.rs/actix/0.13.5/actix/struct.Addr.html

Returns a downgraded WeakAddr.

```APIDOC
### pub fn downgrade(&self) -> WeakAddr<A>

Returns a downgraded WeakAddr.
```

--------------------------------

### Create a leaf future from a Result

Source: https://docs.rs/actix/0.13.5/actix/fut/future/result/fn.result.html

Demonstrates creating futures that resolve immediately with either Ok or Err values using the actix::fut::result function.

```rust
use actix::{fut, Actor, Context};

struct MyActor;
impl Actor for MyActor {
    type Context = Context<Self>;
}

let future_of_1 = fut::result::<u32, u32>(Ok(1));
let future_of_err_2 = fut::result::<u32, u32>(Err(2));
```

--------------------------------

### Response::fut<T>

Source: https://docs.rs/actix/0.13.5/actix/prelude/struct.Response.html

Creates an asynchronous response from a future.

```APIDOC
## pub fn fut<T>(fut: T) -> Self

### Description
Creates an asynchronous response from a provided future.

### Parameters
- **fut** (T) - Required - A future that resolves to the response type I, where T: Future<Output = I> + 'static.
```
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