### Defining Basic Configuration and Extension in Elixir with ExConf

Source: https://github.com/phoenixframework/ex_conf/blob/master/README.md

This snippet demonstrates how to define a basic configuration module using `use ExConf.Config`, set configuration values with the `config` macro, and access them. It also shows how to create a new configuration module that extends an existing one, allowing for overrides while inheriting defaults.

```Elixir
defmodule MyApp.Config do
  use ExConf.Config

  config :router, ssl: true,
                  domain: "example.dev",
                  port: System.get_env("PORT")

  config :session, secret: "secret"
end

iex> MyApp.Config.router[:domain]
"example.dev"


defmodule MyApp.OtherConfig do
  use MyApp.Config

  config :session, secret: "123password"
end

iex> MyApp.OtherConfig.session[:secret]
"123password"
iex> MyApp.OtherConfig.router[:ssl]
true
```

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

### Defining Base Configuration for Environment Lookup in Elixir with ExConf

Source: https://github.com/phoenixframework/ex_conf/blob/master/README.md

This code defines a base configuration module using `ExConf.Config` and specifies an environment variable (`env_var: "MIX_ENV"`) that ExConf should use to determine the current environment at runtime. This base module provides default settings that can be overridden by environment-specific submodules.

```Elixir
defmodule MyApp.Config do
  use ExConf.Config, env_var: "MIX_ENV"

  config :router, ssl: true
  config :twitter, api_token: System.get_env("API_TOKEN")
end
```

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

### Defining Environment-Specific Configuration in Elixir with ExConf

Source: https://github.com/phoenixframework/ex_conf/blob/master/README.md

This snippet shows how to define a configuration module specific to an environment (e.g., `Dev`) by extending the base configuration module (`MyApp.Config`). This submodule provides settings that override the base configuration when the specified environment variable matches its name (capitalized). The `MyApp.Config.env/0` function is used to access the configuration for the currently active environment.

```Elixir
defmodule MyApp.Config.Dev do
  use MyApp.Config

  config :router, ssl: false
  config :twitter, api_token: "ABC"
end

iex> System.get_env("MIX_ENV")
"dev"

iex> MyApp.Config.env
MyApp.Config.Dev

iex> MyApp.Config.env.router[:ssl]
false
```

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