Game Components

A second useful decoupling pattern in MonoGame is the use of game components. You’ve probably noticed that many of the classes you have written have a similar pattern: they each have a LoadContent(), Update(), and Draw() method, and these often take the same arguments. In your game class, you probably mostly invoke these methods for each class in turn. MonoGame provides the concept of game components to help manage this task. This involves: 1) a GameComponentCollection which game components are registered with, and components are implemented by extending the GameComponent or DrawableGameComponent base classes.

The Game implements a GameCollection in its Components property. It will iterate through all components it holds, invoking the Update() and Draw() methods within the game loop.

GameComponent

The GameComponent base class implements IGameComponent, IUpdatable, and IDisposable interfaces. It has the following properties:

• Enabled - this boolean indicates if the component will be updated
• Game - the game this component belongs to
• UpdateOrder - an integer used to sort the order in which game component’s Update() method is invoked

It also has the following virtual methods, which can be overridden:

• Dispose(bool disposing) - Disposes of the component
• Initialize() - Initializes the component; used to set/load any non-graphical content; invoked during the game’s initialization step
• Update(GameTime gameTime) - Invoked every pass through the game loop

Finally, it also implements the following events:

• EnabledChanged - triggered when the Enabled property changes
• UpdateOrderChanged - triggered when the UpdateOrder property changes

DrawableGameComponent

The DrawableGameComponent inherits from the GameComponent base class, and additionally implements the IDrawable interface. In addition to its inherited properties, it declares:

• DrawOrder - an integer that determines the order game components are drawn in
• GraphicsDevice - the graphics device used to draw the game component
• Visible - a boolean that determines if the game component should be drawn

It also has the additional virtual methods:

• LoadContent() - Loads graphical content, invoked by the game during its content loading step
• Draw(GameTime gameTime) - Draws the game component, invoked during the game loop

Finally, it implements the additional properties:

• DrawOrderChanged - triggered when the DrawOrder property changes
• VisibleChanged - triggered when the Visible property changes