### Starting Global and Local Processes in 4D

Source: https://developer.4d.com/docs/18/Concepts/identifiers

Illustrates how to start global and local processes using the New process command. The first example starts a global process, and the second starts a local process.

```4D
//Starting the global process "Add Customers"  
$vlProcessID:=New process("P_ADD_CUSTOMERS";48*1024;"Add Customers")  
```

```4D
//Starting the local process "$Follow Mouse Moves"  
$vlProcessID:=New process("P_MOUSE_SNIFFER";16*1024;"$Follow Mouse Moves")  
```

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

### Example Query with $queryplan

Source: https://developer.4d.com/docs/18/REST/queryplan

This example shows how to pass the $queryplan parameter in a GET request to retrieve the query plan for a filter operation.

```http
GET  /rest/People/$filter="employer.name=acme AND lastName=Jones"&$queryplan=true
```

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

### Basic Error-Handling Method Example

Source: https://developer.4d.com/docs/18/Concepts/error-handling

A simple example demonstrating how to install an error-handling method, execute code, and then disable error catching. The errorMethod project method logs specific errors.

```4D
//installing the error handling method  
 ON ERR CALL("errorMethod")  
 //... executing code  
ON ERR CALL("") //giving control back to 4D  
```

```4D
// errorMethod project method  
 If(Error#1006) //this is not a user interruption  
    ALERT("The error "+String(Error)+" occurred". The code in question is: """+Error formula+""")  
 End if  
```

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

### Using Collection and Object Methods

Source: https://developer.4d.com/docs/18/Concepts/quick-tour

Shows how to use collection and object methods with dot notation. Examples include creating a collection and slicing it, and getting the last employee.

```4D
$c:=New collection(1;2;3;4;5)  
$nc:=$c.slice(0;3) //$nc=[1,2,3]    
  
$lastEmployee:=$employee.last()  
```

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

### Example REST GET Request with Query Parameters

Source: https://developer.4d.com/docs/18/REST/REST_requests

Demonstrates a GET request to a Person dataclass with a filter, method, and timeout parameter. Values can be quoted for clarity.

```http
GET  /rest/Person/?$filter="lastName!=Jones"&$method=entityset&$timeout=600
```

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

### SEND PACKETS Project Method Example

Source: https://developer.4d.com/docs/18/Concepts/parameters

This example demonstrates how a project method can accept a fixed time parameter followed by a variable number of text parameters using parameter indirection.

```4D
//SEND PACKETS Project Method
//SEND PACKETS ( Time ; Text { ; Text2... ; TextN } )
//SEND PACKETS ( docRef ; Data { ; Data2... ; DataN } )

C_TIME($1)
C_TEXT(${2})
C_LONGINT($vlPacket)

For($vlPacket;2;Count parameters)
    SEND PACKET($1;${$vlPacket})
End for

```

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

### Looping Through a Collection with Begin and End Parameters

Source: https://developer.4d.com/docs/18/Concepts/looping

This example illustrates using the begin and end parameters to control the iteration range of a collection. It demonstrates how to append elements to another collection based on specified start and end indices, including negative index calculations.

```4D
 C_COLLECTION($col;$col2)
 $col:=New collection("a";"b";"c";"d";"e")
 $col2:=New collection(1;2;3)
 C_TEXT($item)
 For each($item;$col;0;3)
    $col2.push($item)
 End for each
  //$col2=[1,2,3,"a","b","c"]
 For each($item;$col;-2;-1)
    $col2.push($item)
 End for each
  //$col2=[1,2,3,"a","b","c","d"]
```

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

### Line JSON Example with startPoint

Source: https://developer.4d.com/docs/18/FormObjects/shapesOverview

Defines a static line object for a 4D form, including its starting point and dashed style. The startPoint property is not visible in the Property List.

```json
 "myLine": {
  "type": "line",                  
  "left": 20,  
  "top": 40,  
  "width": 100,  
  "height": 80,
  "startPoint": "topLeft", 
  "strokeDashArray": "6 2" 
  }

```

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

### Install Error-Handling Method

Source: https://developer.4d.com/docs/18/Concepts/error-handling

Installs a custom project method to handle errors in the current process. Call with an empty string to disable error catching.

```4D
ON ERR CALL("IO_ERRORS") //Installs the error-handling method  

ON ERR CALL("") //gives back control to 4D  
```

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

### Repeat...Until Loop Example

Source: https://developer.4d.com/docs/18/Concepts/looping

This example adds a record and then checks if the user wants to continue. Unlike While...End while, initialization of the condition is not required before the loop.

```4D
Repeat
   ADD RECORD([aTable])
Until(OK=0)
```

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

### Example of Modifying a Customer Record

Source: https://developer.4d.com/docs/18/Concepts/methods

This code snippet demonstrates the steps to find a customer using query by example, set the input form, and modify the record. It is intended to be encapsulated within a project method for reuse.

```4D
QUERY BY EXAMPLE([Customers])
FORM SET INPUT([Customers];"Data Entry")
MODIFY RECORD([Customers])
```

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

### Using 4D Commands with Parameters

Source: https://developer.4d.com/docs/18/Concepts/quick-tour

Demonstrates how to use 4D commands with parameters, which are passed in brackets and separated by semicolons. This example copies a document.

```4D
COPY DOCUMENT("folder1\\name1";"folder2\\" ; "new")  
```

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

### Infinite While Loop Example

Source: https://developer.4d.com/docs/18/Concepts/looping

This example demonstrates an infinite loop where the condition NeverStop is always TRUE. Use tracing facilities to manage such situations.

```4D
NeverStop:=True
While(NeverStop)
End while
```

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

### Retrieve Company Data as Array

Source: https://developer.4d.com/docs/18/REST/asArray

This example demonstrates how to fetch company data using the $asArray query option to get the results in an array format. It includes filtering by name and limiting the number of results.

```APIDOC
## GET /rest/Company/

### Description
Returns the result of a query in an array (i.e. a collection) instead of a JSON object.

### Method
GET

### Endpoint
/rest/Company/

### Query Parameters
- **$filter** (string) - Optional - Filters the results based on a specified condition (e.g., "name begin a").
- **$top** (integer) - Optional - Limits the number of results returned (e.g., 3).
- **$asArray** (boolean) - Optional - If set to true, the response will be formatted as an array of objects. Defaults to false.

### Request Example
`GET /rest/Company/?$filter="name begin a"&$top=3&$asArray=true`

### Response
#### Success Response (200)
- The response will be a JSON array where each element is an object representing a company record.

#### Response Example
```json
[
  {
    "__KEY": 15,
    "__STAMP": 0,
    "ID": 15,
    "name": "Alpha North Yellow",
    "creationDate": "!!0000-00-00!!",
    "revenues": 82000000,
    "extra": null,
    "comments": "",
    "__GlobalStamp": 0
  },
  {
    "__KEY": 34,
    "__STAMP": 0,
    "ID": 34,
    "name": "Astral Partner November",
    "creationDate": "!!0000-00-00!!",
    "revenues": 90000000,
    "extra": null,
    "comments": "",
    "__GlobalStamp": 0
  },
  {
    "__KEY": 47,
    "__STAMP": 0,
    "ID": 47,
    "name": "Audio Production Uniform",
    "creationDate": "!!0000-00-00!!",
    "revenues": 28000000,
    "extra": null,
    "comments": "",
    "__GlobalStamp": 0
  }
]
```
```

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

### Default JSON Response Example

Source: https://developer.4d.com/docs/18/REST/asArray

This example shows the same data in its default JSON format, which includes metadata like __entityModel, __COUNT, and __FIRST, with entities nested within an __ENTITIES array.

```JSON
{
  "__entityModel": "Company",
  "__GlobalStamp": 50,
  "__COUNT": 52,
  "__FIRST": 0,
  "__ENTITIES": [
    {
      "__KEY": "15",
      "__TIMESTAMP": "2018-03-28T14:38:07.434Z",
      "__STAMP": 0,
      "ID": 15,
      "name": "Alpha North Yellow",
      "creationDate": "0!0!0",
      "revenues": 82000000,
      "extra": null,
      "comments": "",
      "__GlobalStamp": 0,
      "employees": {
        "__deferred": {
          "uri": "/rest/Company(15)/employees?$expand=employees"
        }
      }
    },
    {
      "__KEY": "34",
      "__TIMESTAMP": "2018-03-28T14:38:07.439Z",
      "__STAMP": 0,
      "ID": 34,
      "name": "Astral Partner November",
      "creationDate": "0!0!0",
      "revenues": 90000000,
      "extra": null,
      "comments": "",
      "__GlobalStamp": 0,
      "employees": {
        "__deferred": {
          "uri": "/rest/Company(34)/employees?$expand=employees"
        }
      }
    },
    {
      "__KEY": "47",
      "__TIMESTAMP": "2018-03-28T14:38:07.443Z",
      "__STAMP": 0,
      "ID": 47,
      "name": "Audio Production Uniform",
      "creationDate": "0!0!0",
      "revenues": 28000000,
      "extra": null,
      "comments": "",
      "__GlobalStamp": 0,
      "employees": {
        "__deferred": {
          "uri": "/rest/Company(47)/employees?$expand=employees"
        }
      }
    }
  ],
  "__SENT": 3
}
```

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

### If Else End if Statement Example

Source: https://developer.4d.com/docs/18/Concepts/branching

Presents the equivalent logic of the 'Case of' example using nested 'If...Else...End if' statements.

```4D
 If(vResult=1) //Test if the number is 1 
    ALERT("One.") //If it is 1, display an alert 
 Else 
    If(vResult=2) //Test if the number is 2 
       ALERT("Two.") //If it is 2, display an alert 
    Else 
       If(vResult=3) //Test if the number is 3 
          ALERT("Three.") //If it is 3, display an alert 
       Else //If it is not 1, 2, or 3, display an alert 
          ALERT("It was not one, two, or three.") 
       End if 
    End if 
 End if  

```

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

### Using a 4D Plug-in Command

Source: https://developer.4d.com/docs/18/Concepts/quick-tour

Illustrates calling a command from a 4D plug-in. This example uses a hypothetical PDF plug-in to remove a page.

```4D
PDF REMOVE PAGE(path;page)  
```

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

### Enable 'Start a New Process' for Menu Command

Source: https://developer.4d.com/docs/18/Menus/properties

Control whether a menu command executes in a new process using the SET MENU ITEM PROPERTY command with the 'Start a New Process' property.

```4D
SET MENU ITEM PROPERTY("MyMenuItem"; "Start a New Process"; "1")
```

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

### Retrieving all attributes from related entities (Company example)

Source: https://developer.4d.com/docs/18/REST/attributes

This example shows how to retrieve all attributes from the 'employees' related entities by using '$attributes=employees.*'.

```APIDOC
## GET /rest/Company(1)/?$attributes=employees.*

### Description
Allows selecting all attributes from related entities. This example retrieves all attributes for the 'employees' relation of a Company entity.

### Method
GET

### Endpoint
/rest/Company(1)/?$attributes=employees.*

### Parameters
#### Query Parameters
- **$attributes** (string) - Required - Defines the path of attributes whose values you want to get for the related entity or entities. Use `*` to retrieve all attributes.

### Response
#### Success Response (200)
(Response structure will include all attributes for each employee)

### Response Example
(Response will be similar to the previous example but include all fields for each employee)
```

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

### Example Usage of Capitalize_text Method

Source: https://developer.4d.com/docs/18/Concepts/string

Demonstrates how to call the Capitalize_text project method and display the result using an ALERT box.

```4D
ALERT(Capitalize_text("hello, my name is jane doe and i'm running for president!"))  
```

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

### Get Distinct Company Names Starting with 'a'

Source: https://developer.4d.com/docs/18/REST/distinct

Retrieves a list of unique company names that begin with the letter 'a'. This example demonstrates the basic usage of the $distinct parameter with a $filter.

```HTTP
GET /rest/Company/name?$filter="name=a*"&$distinct=true
```

```JSON
[
    "Adobe",
    "Apple"
]
```

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

### Declaring a Date Variable

Source: https://developer.4d.com/docs/18/Concepts/quick-tour

Shows how to formally create a typed variable using the C_XXX command. This example declares a variable of the date type.

```4D
C_DATE(MyDate) //Date type for MyDate variable  
```

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

### Calling Project Methods

Source: https://developer.4d.com/docs/18/Concepts/identifiers

Demonstrates how to call project methods. Method names can be used directly. Some commands expect method names as strings.

```4D
If(New client)
DELETE DUPLICATED VALUES
APPLY TO SELECTION([Employees];INCREASE SALARIES)
```

```4D
//This command expects a method (function) or formula
QUERY BY FORMULA([aTable];Special query)
//This command expects a method (procedure) or statement
APPLY TO SELECTION([Employees];INCREASE SALARIES)
//But this command expects a method name
ON EVENT CALL("HANDLE EVENTS")
```

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

### Skip to the 20th Entity

Source: https://developer.4d.com/docs/18/REST/skip

Use the $skip query option to start retrieving entities from a specific position in the collection. This example retrieves entities starting from the 20th.

```http
GET  /rest/Employee/$entityset/CB1BCC603DB0416D939B4ED379277F02?$skip=20
```

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

### Line JSON Example with different startPoint

Source: https://developer.4d.com/docs/18/FormObjects/shapesOverview

Demonstrates an alternative configuration for a static line object in a 4D form, using a different startPoint and dashed line style.

```json
 "myLine": {
  "type": "line",                  
  "left": 20,  
  "top": 40,  
  "width": 100,  
  "height": 80,
  "startPoint": "bottomLeft", 
  "strokeDashArray": "6 2" 
  }

```

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

### Accessing nested related attributes (Employee example)

Source: https://developer.4d.com/docs/18/REST/attributes

This example demonstrates how to access attributes of a nested related entity, such as getting the 'lastname' of employees related to an employer.

```APIDOC
## GET /rest/Employee(1)?$attributes=employer.employees.lastname

### Description
Allows accessing attributes of nested related entities. This example retrieves the 'lastname' of all 'employees' related to the 'employer' of a given Employee.

### Method
GET

### Endpoint
/rest/Employee(1)?$attributes=employer.employees.lastname

### Parameters
#### Query Parameters
- **$attributes** (string) - Required - Defines the path of attributes whose values you want to get for nested related entities. Use dot notation to traverse relations.

### Response
#### Success Response (200)
(Response structure will show the employer, and within it, a list of employees with their lastnames)

### Response Example
(Response will show the employer object, and nested within it, an 'employees' array containing objects with a 'lastname' field for each employee.)
```

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

### Display "Hello, World!" Message

Source: https://developer.4d.com/docs/18/Concepts/quick-tour

Use the ALERT command to display a platform-standard alert dialog box with a message. This is the simplest way to show a message to the user.

```4D
ALERT("Hello, World!")  
```

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

### Project Methods with Parameters and Return Values

Source: https://developer.4d.com/docs/18/Concepts/identifiers

Illustrates how project methods can accept parameters passed in parentheses and separated by semicolons. Local variables $1, $2, etc., are used for parameters, and $0 is used for the return value in functions.

```4D
//Within DROP SPACES $1 is a pointer to the field [People]Name
DROP SPACES(->[People]Name)
```

```4D
//Within Calc creator:
//- $1 is numeric and equal to 1
//- $2 is numeric and equal to 5
//- $3 is text or string and equal to "Nice"
//- The result value is assigned to $0
$vsResult:=Calc creator(1;5;"Nice")
```

```4D
//Within Dump:
//- The three parameters are text or string
//- They can be addressed as $1, $2 or $3
//- They can also be addressed as, for instance, ${$vlParam} where $vlParam is 1, 2 or 3
//- The result value is assigned to $0
vtClone:=Dump("is";"the";"it")
```

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

### Declaring Generic Parameters

Source: https://developer.4d.com/docs/18/Concepts/parameters

Example of declaring generic parameters using a compiler directive to specify the data type for a range of parameters starting from a specific index.

```4D
C_LONGINT(${4})

```

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

### Example Query with $querypath (No Entities Found)

Source: https://developer.4d.com/docs/18/REST/querypath

Demonstrates how to use the $querypath parameter when no entities are found. The response shows the query path taken by 4D Server.

```http
GET  /rest/Employee/$filter="employer.name=acme AND lastName=Jones"&$querypath=true
```

```http
GET  /rest/$querypath
```

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

### Apply Yellow Letters to Text Objects with Text Attribute Starting With 'Hello'

Source: https://developer.4d.com/docs/18/FormEditor/stylesheets

Use the [attribute|="value"] selector to match objects where an attribute's value begins with a specific string. This example targets 'text' type objects where the 'text' attribute starts with 'Hello'.

```css
text[text|=Hello]
{
     stroke: yellow;
}
```

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

### Retrieve Company Data as Array

Source: https://developer.4d.com/docs/18/REST/asArray

Use the $asArray=true parameter in your REST request to get the response in an array format. This example filters companies by name and limits the results.

```HTTP
GET  /rest/Company/?$filter="name begin a"&$top=3&$asArray=true
```

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

### Example Query with $querypath (Entities Found)

Source: https://developer.4d.com/docs/18/REST/querypath

Shows a query using $querypath where at least one entity is found. The subsequent $querypath call will reflect the executed path.

```http
GET  /rest/Employee/$filter="employer.name=a* AND lastName!=smith"&$querypath=true
```

```http
GET  /rest/$querypath
```

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

### Dataclass Employee Information Response

Source: https://developer.4d.com/docs/18/REST/catalog

This is an example JSON response for a GET request to retrieve information about the 'Employee' dataclass. It details the dataclass's properties, attributes, and primary key.

```JSON
{
    name: "Employee",
    className: "Employee",
    collectionName: "EmployeeCollection",
    scope: "public",
    dataURI: "http://127.0.0.1:8081/rest/Employee",
    defaultTopSize: 20,
    extraProperties: {
        panelColor: "#76923C",
        __CDATA: "\n\n\t\t\n",
        panel: {
            isOpen: "true",
            pathVisible: "true",
            __CDATA: "\n\n\t\t\t\n",
            position: {
                X: "394",
                Y: "42"
            }
        }
    },
    attributes: [
        {
            name: "ID",
            kind: "storage",
            scope: "public",
            indexed: true,
            type: "long",
            identifying: true
        },
        {
            name: "firstName",
            kind: "storage",
            scope: "public",
            type: "string"
        },
        {
            name: "lastName",
            kind: "storage",
            scope: "public",
            type: "string"
        },
        {
            name: "fullName",
            kind: "calculated",
            scope: "public",
            type: "string",
            readOnly: true
        },
        {
            name: "salary",
            kind: "storage",
            scope: "public",
            type: "number",
            defaultFormat: {
                format: "$###,###.00"
            }
        },
        {
            name: "photo",
            kind: "storage",
            scope: "public",
            type: "image"
        },
        {
            name: "employer",
            kind: "relatedEntity",
            scope: "public",
            type: "Company",
            path: "Company"
        },
        {
            name: "employerName",
            kind: "alias",
            scope: "public",

            type: "string",
            path: "employer.name",
            readOnly: true
        },
        {
            name: "description",
            kind: "storage",
            scope: "public",
            type: "string",
            multiLine: true
        },
   ],
    key: [
        {
            name: "ID"
        }
    ]
}
```

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

### Addressing Array Elements in 4D

Source: https://developer.4d.com/docs/18/Concepts/identifiers

Demonstrates how to access elements in interprocess, process, and local arrays using curly braces with a numeric index. The last example shows how to get the size of an array.

```4D
//Addressing an element of an interprocess array  
If(<>asKeywords{1}="Stop")  
<>atSubjects{$vlElem}:=[Topics]Subject  
$viNextValue:=<>aiBigArray{Size of array(<>aiBigArray)}  
  
 //Addressing an element of a process array  
If(asKeywords{1}="Stop")  
atSubjects{$vlElem}:=[Topics]Subject  
$viNextValue:=aiBigArray{Size of array(aiBigArray)}  
  
 //Addressing an element of a local array  
If($asKeywords{1}="Stop")  
$atSubjects{$vlElem}:=[Topics]Subject  
$viNextValue:=$aiBigArray{Size of array($aiBigArray)}  
```

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

### Retrieve Related Entities

Source: https://developer.4d.com/docs/18/REST/method

This example demonstrates how to retrieve related entities for a specific entity using a GET request. It shows how to expand the 'staff' relation attribute in the Company dataclass linked to the Employee dataclass.

```APIDOC
## GET /rest/Company(1)/staff

### Description
Retrieves related entities for a specific company, expanding the 'staff' relation.

### Method
GET

### Endpoint
/rest/Company(1)/staff

### Query Parameters
- **$expand** (string) - Optional - Specifies related entities to expand, e.g., 'staff'.
- **$method** (string) - Optional - Set to 'subentityset' to retrieve a sub-entity set.
- **$subOrderby** (string) - Optional - Specifies the order for sub-entity sets, e.g., 'lastName ASC'.

### Response
#### Success Response (200)
Returns a JSON object containing a list of related entities (employees in this case) with their details.

#### Response Example
```json
{
  "__ENTITYSET": "/rest/Employee/$entityset/FF625844008E430B9862E5FD41C741AB",
  "__entityModel": "Employee",
  "__COUNT": 2,
  "__SENT": 2,
  "__FIRST": 0,
  "__ENTITIES": [
    {
      "__KEY": "4",
      "__STAMP": 1,
      "ID": 4,
      "firstName": "Linda",
      "lastName": "Jones",
      "birthday": "1970-10-05T14:23:00Z",
      "employer": {
        "__deferred": {
          "uri": "/rest/Company(1)",
          "__KEY": "1"
        }
      }
    },
    {
      "__KEY": "1",
      "__STAMP": 3,
      "ID": 1,
      "firstName": "John",
      "lastName": "Smith",
      "birthday": "1985-11-01T15:23:00Z",
      "employer": {
        "__deferred": {
          "uri": "/rest/Company(1)",
          "__KEY": "1"
        }
      }
    }
  ]
}
```
```

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

### While Loop with User Confirmation

Source: https://developer.4d.com/docs/18/Concepts/looping

This example uses a While loop that continues as long as the user confirms adding a record. The OK system variable is controlled by user interaction and record saving.

```4D
CONFIRM("Add a new record?")
While(OK=1)
   ADD RECORD([aTable])
End while
```

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

### Get Employee Photo with Specific Version

Source: https://developer.4d.com/docs/18/REST/version

This example defines the image format as JPEG and passes the actual version number sent by the server to retrieve an employee's photo. The $version parameter helps bypass browser cache.

```http
GET  /rest/Employee(1)/photo?$imageformat=jpeg&$version=3&$expand=photo
```

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

### Calling ALERT with Optional Parameters

Source: https://developer.4d.com/docs/18/Concepts/parameters

Illustrates calling the ALERT command with one or two parameters, demonstrating the use of optional parameters.

```4D
ALERT("Are you sure?";"Yes I am") //2 parameters  
ALERT("Time is over") //1 parameter  

```

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

### Array Response Example

Source: https://developer.4d.com/docs/18/REST/asArray

This is an example of the response received when using the $asArray=true parameter. The data is structured as a JSON array of objects.

```JSON
[
  {
    "__KEY": 15,
    "__STAMP": 0,
    "ID": 15,
    "name": "Alpha North Yellow",
    "creationDate": "!!0000-00-00!!",
    "revenues": 82000000,
    "extra": null,
    "comments": "",
    "__GlobalStamp": 0
  },
  {
    "__KEY": 34,
    "__STAMP": 0,
    "ID": 34,
    "name": "Astral Partner November",
    "creationDate": "!!0000-00-00!!",
    "revenues": 90000000,
    "extra": null,
    "comments": "",
    "__GlobalStamp": 0
  },
  {
    "__KEY": 47,
    "__STAMP": 0,
    "ID": 47,
    "name": "Audio Production Uniform",
    "creationDate": "!!0000-00-00!!",
    "revenues": 28000000,
    "extra": null,
    "comments": "",
    "__GlobalStamp": 0
  }
]
```

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

### Calling a Project Method with Multiple Parameters

Source: https://developer.4d.com/docs/18/Concepts/parameters

Shows how to call a custom project method named DO SOMETHING with three distinct parameters.

```4D
DO SOMETHING(WithThis;AndThat;ThisWay)  

```

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

### Retrieving all attributes from a related entity (Employee example)

Source: https://developer.4d.com/docs/18/REST/attributes

This example shows how to retrieve all attributes from the 'employer' related entity by using '$attributes=employer.*'.

```APIDOC
## GET /rest/Employee(1)?$attributes=employer.*

### Description
Allows selecting all attributes from a related entity. This example retrieves all attributes for the 'employer' relation of an Employee entity.

### Method
GET

### Endpoint
/rest/Employee(1)?$attributes=employer.*

### Parameters
#### Query Parameters
- **$attributes** (string) - Required - Defines the path of attributes whose values you want to get for the related entity. Use `*` to retrieve all attributes.

### Response
#### Success Response (200)
(Response structure will include all attributes for the employer)

### Response Example
(Response will be similar to the previous example but include all fields for the employer)
```

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

### Call Project Method with Return Value

Source: https://developer.4d.com/docs/18/Concepts/quick-tour

Demonstrates calling a project method ('Do_Something') and assigning its return value to a variable. The called method uses $1 for input and $0 for the return value. Ensure the 'Do_Something' method is defined in your project.

```4D
$myText:="hello" 
$myText:=Do_Something($myText) //Call the Do_Something method 
ALERT($myText) //"HELLO" 

  //Here the code of the method Do_Something 
$0:=Uppercase($1)
```

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

### Example JSON Result Structure

Source: https://developer.4d.com/docs/18/REST/orderby

This is an example of the JSON structure returned when querying entities, showing the __ENTITIES array which contains the sorted data.

```JSON
{
    __entityModel: "Employee",
    __COUNT: 10,
    __SENT: 10,
    __FIRST: 0,
    __ENTITIES: [
        {
            __KEY: "1",
            __STAMP: 1,
            firstName: "John",
            lastName: "Smith",
            salary: 90000
        },
        {
            __KEY: "2",
            __STAMP: 2,
            firstName: "Susan",
            lastName: "O'Leary",
            salary: 80000
        },
// more entities
    ]
}
```

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

### Using Collection Methods: Copy and Push

Source: https://developer.4d.com/docs/18/Concepts/collection

Demonstrates the usage of collection member functions like 'copy' for deep copying and 'push' for adding elements to a collection.

```4D
$newCol:=$col.copy() //deep copy of $col to $newCol  
$col.push(10;100) //add 10 and 100 to the collection  
```

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

### Using Predefined Constants

Source: https://developer.4d.com/docs/18/Concepts/quick-tour

Demonstrates the use of predefined constants to improve code readability. This example opens a document in read-only mode using the 'Read Mode' constant.

```4D
vRef:=Open document("PassFile";"TEXT";Read Mode) // open doc in read only mode  
```

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

### GET /$catalog/{dataClass}

Source: https://developer.4d.com/docs/18/REST/catalog

Returns information about a specific data class and its attributes. Use this endpoint to get details for a single data class.

```APIDOC
## GET /$catalog/{dataClass}

### Description
Returns information about a specific data class and its attributes. Use this endpoint to get details for a single data class.

### Method
GET

### Endpoint
/rest/$catalog/{dataClass}

### Parameters
#### Path Parameters
- **dataClass** (string) - Required - The name of the data class for which to retrieve information.

### Response
#### Success Response (200)
- **name** (string) - Name of the data class.
- **collectionName** (string) - Name of an entity selection on the data class.
- **tableNumber** (number) - Table number in the 4D database.
- **scope** (string) - Scope for the data class (e.g., "public").
- **dataURI** (string) - A URI to the data in the data class.
- **attributes** (array) - An array of attribute objects associated with the data class.
  - **name** (string) - Name of the attribute.
  - **kind** (string) - The kind of attribute (e.g., "storage", "relatedEntities").
  - **fieldPos** (number) - Field position in the data class.
  - **scope** (string) - Scope of the attribute (e.g., "public").
  - **indexed** (boolean) - Indicates if the attribute is indexed.
  - **type** (string) - Data type of the attribute (e.g., "long", "string", "number").
  - **identifying** (boolean) - Indicates if the attribute is part of the primary key.
  - **reversePath** (boolean) - Indicates if a reverse path exists for related entities.
  - **path** (string) - The path for related entities.
- **key** (array) - An array of objects representing the primary key of the data class.
  - **name** (string) - The name of the key attribute.
```

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

### While Loop Equivalent for 100 Iterations

Source: https://developer.4d.com/docs/18/Concepts/looping

Demonstrates how to achieve the same result as a basic For loop using a While loop. Requires manual counter initialization and increment.

```4D
$i:=1 //Initialize the counter
While($i<=100) //Loop 100 times
  //Do something
    $i:=$i+1 //Need to increment the counter
End while
```

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

### Example Response for Retrieving Related Entities

Source: https://developer.4d.com/docs/18/REST/method

This is an example of the JSON response structure when retrieving related entities, showing entity details and count information.

```JSON
{
   
    "__ENTITYSET": "/rest/Employee/$entityset/FF625844008E430B9862E5FD41C741AB",  
    "__entityModel": "Employee",  
    "__COUNT": 2,  
    "__SENT": 2,  
    "__FIRST": 0,  
    "__ENTITIES": [
        {
            "__KEY": "4",
            "__STAMP": 1,
            "ID": 4,
            "firstName": "Linda",
            "lastName": "Jones",
            "birthday": "1970-10-05T14:23:00Z",
            "employer": {
                "__deferred": {
                    "uri": "/rest/Company(1)",
                    "__KEY": "1"
                }
            }
        },
        {
            "__KEY": "1",
            "__STAMP": 3,
            "ID": 1,
            "firstName": "John",
            "lastName": "Smith",
            "birthday": "1985-11-01T15:23:00Z",
            "employer": {
                "__deferred": {
                    "uri": "/rest/Company(1)",
                    "__KEY": "1"
                }
            }
        }
    ] 
   
}
```

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

### Calling a Plug-In Command

Source: https://developer.4d.com/docs/18/Concepts/identifiers

Shows how to call a plug-in command using its name as defined by the plug-in. Plug-in command names can be up to 31 characters.

```4D
$error:=SMTP_From($smtp_id;"henry@gmail.com")
```

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

### Example: User Input Validation

Source: https://developer.4d.com/docs/18/Concepts/branching

Demonstrates using If...Else...End if to process user input, querying a database or alerting the user.

```4D
 // Ask the user to enter a name
 $Find:=Request(Type a name)
 If(OK=1)
  QUERY([People];[People]LastName=$Find)
 Else
  ALERT("You did not enter a name.")
 End if
```

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

### Pointer Creation and Dereferencing

Source: https://developer.4d.com/docs/18/Concepts/quick-tour

Shows how to create a pointer to a variable ('MyPointer') and then dereference it to access the variable's value using 'ALERT()'. This demonstrates pointer usage.

```4D
MyVar:="Hello"
MyPointer:=->MyVar
ALERT(MyPointer->)
```

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

### Selecting specific attributes from a related entity (Employee example)

Source: https://developer.4d.com/docs/18/REST/attributes

This example shows how to retrieve a specific attribute ('name') from a single related entity ('employer') of an Employee.

```APIDOC
## GET /rest/Employee(1)?$attributes=employer.name

### Description
Allows selecting specific attributes from a related entity. This example retrieves the 'name' attribute from the 'employer' relation of an Employee entity.

### Method
GET

### Endpoint
/rest/Employee(1)?$attributes=employer.name

### Parameters
#### Query Parameters
- **$attributes** (string) - Required - Defines the path of attributes whose values you want to get for the related entity. For a single related entity, use the format `relatedEntity.attributePath`.

### Response
#### Success Response (200)
- **__entityModel** (string) - The entity model name.
- **__KEY** (string) - The primary key of the entity.
- **__TIMESTAMP** (string) - The timestamp of the entity.
- **__STAMP** (integer) - The stamp of the entity.
- **employer** (object) - An object containing information about the related employer.
  - **__KEY** (string) - The primary key of the employer.
  - **__TIMESTAMP** (string) - The timestamp of the employer.
  - **__STAMP** (integer) - The stamp of the employer.
  - **name** (string) - The name attribute of the employer.

### Response Example
```json
{
	"__entityModel": "Employee",
	"__KEY": "1",
	"__TIMESTAMP": "2019-12-01T20:18:26.046Z",
	"__STAMP": 5,
	"employer": {
		"__KEY": "1",
		"__TIMESTAMP": "2018-04-25T14:41:16.237Z",
		"__STAMP": 0,
		"name": "Adobe"
	}
}
```
```

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

### Accessing Host Database Tables from a Component

Source: https://developer.4d.com/docs/18/Concepts/components

Demonstrates how a component can call a host database method to create a record and insert data into a host database table using pointers.

```4D
// calling a component method  
methCreateRec(->[PEOPLE];->[PEOPLE]Name;"Julie Andrews")  
```

```4D
C_POINTER($1) //Pointer on a table in host database  
C_POINTER($2) //Pointer on a field in host database  
C_TEXT($3) // Value to insert  
  
$tablepointer:=$1  
$fieldpointer:=$2  
CREATE RECORD($tablepointer->)  
  
$fieldpointer->:=$3  
SAVE RECORD($tablepointer->)  
```

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

### Get Window Rect in SDI

Source: https://developer.4d.com/docs/18/Menus/sdi

When -1 is passed as the window parameter to the `GET WINDOW RECT` command in SDI mode, it returns 0;0;0;0.

```4D
// When -1 is passed in window parameter, the command returns 0;0;0;0
GET WINDOW RECT(-1)
```

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

### Selecting multiple specific attributes from related entities (Company example)

Source: https://developer.4d.com/docs/18/REST/attributes

This example demonstrates retrieving multiple specific attributes ('lastname', 'jobname') from the 'employees' related entities.

```APIDOC
## GET /rest/Company(1)/?$attributes=employees.lastname,employees.jobname

### Description
Allows selecting multiple specific attributes from related entities. This example retrieves 'lastname' and 'jobname' for the 'employees' relation of a Company entity.

### Method
GET

### Endpoint
/rest/Company(1)/?$attributes=employees.lastname,employees.jobname

### Parameters
#### Query Parameters
- **$attributes** (string) - Required - Defines the path of attributes whose values you want to get for the related entity or entities. Separate multiple attribute paths with a comma.

### Response
#### Success Response (200)
(Response structure will include 'lastname' and 'jobname' for each employee)

### Response Example
(Response will be similar to the first example, but only include 'lastname' and 'jobname' for each employee)
```

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

### Define Row Height Array Example

Source: https://developer.4d.com/docs/18/FormObjects/propertiesCoordinatesAndSizing

Example of how to define and populate a row height array in 4D. This array can then be associated with a list box to control individual row heights.

```4D
ARRAY LONGINT(RowHeights;20)
RowHeights{5}:=3
```

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

### Address and Initialize Individual Bytes of a BLOB in 4D

Source: https://developer.4d.com/docs/18/Concepts/blob

Demonstrates how to set the size of a BLOB and then iterate through its bytes to initialize each one to zero using individual byte addressing.

```4D
  ` Declare a variable of type BLOB  
 C_BLOB(vBlob)  
  ` Set the size of the BLOB to 256 bytes  
 SET BLOB SIZE(vBlob;256)  
  ` The loop below initializes the 256 bytes of the BLOB to zero  
 For(vByte;0;BLOB size(vBlob)-1)  
    vBlob{vByte}:=0  
 End for  
```

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

### Selecting specific attributes from related entities (Company example)

Source: https://developer.4d.com/docs/18/REST/attributes

This example demonstrates how to use the $attributes parameter to retrieve specific attributes (lastname) from a related entity (employees) of a Company.

```APIDOC
## GET /rest/Company(1)/?$attributes=employees.lastname

### Description
Allows selecting the related attribute(s) to get from the dataclass. This example shows retrieving the 'lastname' attribute from the 'employees' relation of a Company entity.

### Method
GET

### Endpoint
/rest/Company(1)/?$attributes=employees.lastname

### Parameters
#### Query Parameters
- **$attributes** (string) - Required - Defines the path of attributes whose values you want to get for the related entity or entities. For related entities, use the format `relatedEntities.attributePath1, relatedEntities.attributePath2, ...`.

### Response
#### Success Response (200)
- **__entityModel** (string) - The entity model name.
- **__KEY** (string) - The primary key of the entity.
- **__TIMESTAMP** (string) - The timestamp of the entity.
- **__STAMP** (integer) - The stamp of the entity.
- **employees** (object) - An object containing information about related employees.
  - **__ENTITYSET** (string) - The entity set URL for the related entities.
  - **__GlobalStamp** (integer) - The global stamp for the related entities.
  - **__COUNT** (integer) - The total count of related entities.
  - **__FIRST** (integer) - The index of the first related entity.
  - **__ENTITIES** (array) - An array of related entity objects.
    - **__KEY** (string) - The primary key of the related entity.
    - **__TIMESTAMP** (string) - The timestamp of the related entity.
    - **__STAMP** (integer) - The stamp of the related entity.
    - **lastname** (string) - The lastname attribute of the employee.

### Response Example
```json
{
    "__entityModel": "Company",
    "__KEY": "1",
    "__TIMESTAMP": "2018-04-25T14:41:16.237Z",
    "__STAMP": 2,
    "employees": {
		"__ENTITYSET": "/rest/Company(1)/employees?$expand=employees",
		"__GlobalStamp": 50,
		"__COUNT": 135,
		"__FIRST": 0,
		"__ENTITIES": [
			{
				"__KEY": "1",
				"__TIMESTAMP": "2019-12-01T20:18:26.046Z",
				"__STAMP": 5,
				"lastname": "ESSEAL"
			},
			{
				"__KEY": "2",
				"__TIMESTAMP": "2019-12-04T10:58:42.542Z",
				"__STAMP": 6,
				"lastname": "JONES"
			},
			...
    }
}
```
```

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

### Method DO SOMETHING receiving Text Parameters

Source: https://developer.4d.com/docs/18/Concepts/parameters

Illustrates the internal code of a method that accepts three text parameters, assigning them to local variables $1, $2, and $3, and then displays them using ALERT.

```4D
//Code of the method DO SOMETHING  
//Assuming all parameters are of the text type  
C_TEXT($1;$2;$3)  
ALERT("I received "+$1+" and "+$2+" and also "+$3)
//$1 contains the WithThis parameter  
//$2 contains the AndThat parameter  
//$3 contains the ThisWay parameter  

```

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

### Using Named Selections in 4D

Source: https://developer.4d.com/docs/18/Concepts/identifiers

Demonstrates how to use named selections in 4D. The first example shows an interprocess named selection, and the second shows a standard process named selection.

```4D
//Interprocess Named Selection  
USE NAMED SELECTION([Customers];"<>ByZipcode")  
```

```4D
//Process Named Selection  
USE NAMED SELECTION([Customers];"<>ByZipcode")  
```

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

### Help Button JSON Configuration

Source: https://developer.4d.com/docs/18/FormObjects/buttonOverview

Configuration for a button with the Help style, typically displayed as a question mark in a circle. This style has limitations on supported properties.

```json
 "myButton": {
                "type": "button",
                "style":"help",
                "text": "OK",
                "dropping": "custom",
                "left": 60,
                "top": 160,
                "width": 100,
                "height": 20
                }

```

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

### Call 4D Method from Web Area

Source: https://developer.4d.com/docs/18/FormObjects/webAreaOverview

Demonstrates calling a 4D method named HelloWorld from a Web area using the $4d JavaScript object.

```javascript
$4d.HelloWorld();
```

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

### Example REST Request to Filter Data

Source: https://developer.4d.com/docs/18/REST/configuration

This example demonstrates how to filter data from an Employee table using a REST request. Ensure the 4D REST server is enabled and the Employee table is exposed.

```http
http://127.0.0.1:8044/rest/Employee/?$filter="salary>10000"
```

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

### Managing Sets in 4D

Source: https://developer.4d.com/docs/18/Concepts/identifiers

Demonstrates the usage of interprocess, process, and client sets. Sets are managed on the Server but can be worked with locally on the Client using client sets.

```4D
//Interprocess sets
USE SET("<>Deleted Records")
CREATE SET([Customers];"<>Customer Orders")
If(Records in set("<>Selection"+String($i))>0)
```

```4D
//Process sets
USE SET("Deleted Records")
CREATE SET([Customers];"Customer Orders")
If(Records in set("<>Selection"+String($i))>0)
```

```4D
//Client sets
USE SET("$Deleted Records")
CREATE SET([Customers];"$Customer Orders")
If(Records in set("$Selection"+String($i))>0)
```

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

### Chaining Collection Methods: Push and Sort

Source: https://developer.4d.com/docs/18/Concepts/collection

Shows how collection methods can be chained, such as using 'push' to add elements and then 'sort' to order them. Some methods return the modified collection, allowing sequential calls.

```4D
$col:=New collection(5;20)
$col2:=$col.push(10;100).sort() //$col2=[5,10,20,100]  
```