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# Actions, Controllers and Results

## What is an Action?

Most of the requests received by a Play application are handled by an `Action`.

A `play.api.mvc.Action` is basically a `(play.api.mvc.Request => play.api.mvc.Result)` function that handles a request and generates a result to be sent to the client.

@[echo-action](code/ScalaActions.scala)

An action returns a `play.api.mvc.Result` value, representing the HTTP response to send to the web client. In this example `Ok` constructs a **200 OK** response containing a **text/plain** response body.

## Building an Action

Within any controller extending `BaseController`, the `Action` value is the default action builder. This action builder contains several helpers for creating `Action`s.

The first simplest one just takes as argument an expression block returning a `Result`:

@[zero-arg-action](code/ScalaActions.scala)

This is the simplest way to create an Action, but we don't get a reference to the incoming request. It is often useful to access the HTTP request calling this Action.

So there is another Action builder that takes as an argument a function `Request => Result`:

@[request-action](code/ScalaActions.scala)

It is often useful to mark the `request` parameter as `implicit` so it can be implicitly used by other APIs that need it:

@[implicit-request-action](code/ScalaActions.scala)

If you have broken up your code into methods, then you can pass through the implicit request from the action:

@[implicit-request-action-with-more-methods](code/ScalaActions.scala)

The last way of creating an Action value is to specify an additional `BodyParser` argument:

@[json-parser-action](code/ScalaActions.scala)

Body parsers will be covered later in this manual.  For now you just need to know that the other methods of creating Action values use a default **Any content body parser**.

## Controllers are action generators

A controller in Play is nothing more than an object that generates `Action` values. Controllers are typically defined as classes to take advantage of [[Dependency Injection|ScalaDependencyInjection]].

> **Note:** Keep in mind that defining controllers as objects will not be supported in future versions of Play. Using classes is the recommended approach.

The simplest use case for defining an action generator is a method with no parameters that returns an `Action` value:

@[full-controller](code/ScalaActions.scala)

Of course, the action generator method can have parameters, and these parameters can be captured by the `Action` closure:

@[parameter-action](code/ScalaActions.scala)

## Simple results

For now we are just interested in simple results: an HTTP result with a status code, a set of HTTP headers and a body to be sent to the web client.

These results are defined by `play.api.mvc.Result`:

@[simple-result-action](code/ScalaActions.scala)

Of course there are several helpers available to create common results such as the `Ok` result in the sample above:

@[ok-result-action](code/ScalaActions.scala)

This produces exactly the same result as before.

Here are several examples to create various results:

@[other-results](code/ScalaActions.scala)

All of these helpers can be found in the `play.api.mvc.Results` trait and companion object.

## Redirects are simple results too

Redirecting the browser to a new URL is just another kind of simple result. However, these result types don't take a response body.

There are several helpers available to create redirect results:

@[redirect-action](code/ScalaActions.scala)

The default is to use a `303 SEE_OTHER` response type, but you can also set a more specific status code if you need one:

@[moved-permanently-action](code/ScalaActions.scala)

## `TODO` dummy page

You can use an empty `Action` implementation defined as `TODO`: the result is a standard ‘Not implemented yet’ result page:

@[todo-action](code/ScalaActions.scala)
