# Actions

Actions are reusable, well, actions which can last longer than an instant. This could be anything from just a delayed action, a soundeffect to a player jump.

An action has its own update function `completed?`. It is called that way because it also returns the state of the action (if it is completed). There also the `on_start` and `on_end` functions which can be overriden and are called on the appropriate times.

An action is initiated via the `App#act` method. First, the `Action#on_start` method is called. After that, the `Action#completed?`function is called every frame until it returns true. Then `Action#on_end` is called and the action removed.

There are builtin actions as well. They are explained in the 'Builtin Actions' chapter of this book.

```ruby
class IntervalAction < Scar::Action
    @elapsed = 0f32
    def initialize(@interval : Float32, @repeats : Int32, @f : Proc(Void))
    end
    
    def completed?(dt)
        return true if @repeats <= 0
        @elapsed += dt
        if @elapsed >= @interval
            f.call
            @repeats -= 1
            @elapsed = 0f32
        end
        return false
    end
end


# Beep every second five times
app.act IntervalAction.new(1f32, 5, -> { app.act Scar::Actions::PlaySound.new(Assets["beep.wav", Assets::Sound]) })
```