# Controllers

See **plug** for more info since controllers are plugs

External data uses string keys, internal data uses atoms

### Actions

All actions take two args:

* `conn`: a struct which holds data about requests
* `params`: request params(seems to everything like post body, query params, and more), Map with **string keys** 

Return values with `json/2`, `text/2`, and `html/2`

To let Phoenix views build resp, use `render/3`

lib/hello\_web/controllers/hello\_controller.ex

```elixir
defmodule HelloWeb.HelloController do
  use HelloWeb, :controller
  import Hello.Auth, only: [logged_in_user: 2]
  #pass through plug with a guard(like middleware)
  plug :logged_in_user when action not in [:new, :create]

  #params are combo of /m/:messenger and query params
  def show(conn, %{"messenger" => messenger}) do
    #gets :messenger from /hello/:messenger route
    #render(conn, "show.html", messenger: messenger) ORRRR
    conn
    |> assign(:messenger, messenger)
    |> render("show.html")
    #find and render show.html.eex in lib/hello_web/templates/hello (named after controller)
  end

  def redirect(conn, _params) do
      conn 
      |> put_flash(:info, "Redirecting")
      |> redirect(to: "/redirect_test")
      #      |> redirect(external: "google.com")
  end

  def get(conn, _params) do
    conn
    |> put_status(401)
    |> json(%{user: 1})
    # |> text("") #is empty 200 resp
  end
end
```

## Flashes

Add server messages

```elixir
conn
|> put_flash(:info, "Welcome to Phoenix, from flash info!")
|> put_flash(:error, "Let's pretend we have an error.")
|> render("index.html")
```

Instead of adding it to the html directly

templates/layout/app.html.eex

```
<meta name="flash-info" content="<%= get_flash(@conn, :info) %>" />
<meta name="flash-danger" content="<%= get_flash(@conn, :error) %>" />
```

App.js

```
useEffect(() => {
  const metaFlashInfo = document.querySelector("meta[name='flash-info']");
  const metaFlashDanger = document.querySelector("meta[name='flash-danger']");

  const toastIfContent = (message) => message && toast(message);

  toastIfContent(metaFlashInfo.content);
  toastIfContent(metaFlashDanger.content);
}, []);
```


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