Dependency Injection

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Dependency Injection Overview

The IoC Container of Swiz is the BeanProvider class. Any beans defined in a registered BeanProvider can be injected into other registered beans or into views added to the display list.

Defining an injection target is done using the [Inject] metadata tag. Common injection scenarios include the following:

• Inject Model into View
• Inject Model into Controller
• Inject Delegate into Controller
• Inject Service into Delegate

Inject by type

If you define exactly one bean of a given type you can inject it into a matching destination with a plain [Inject] tag. Note this also supports injecting a concrete implementation of an interface to which the destination is typed. In other words, if a property decorated with [Inject] is of type IUserService, Swiz will correctly inject a bean implementing that interface, such as UserService or MockUserService.

[Inject]
public var model:IUserModel;

Inject by name

If you have more than one bean of a given type defined you can request that a bean with a specific name be injected. This bean name must match the id attribute of the bean's tag as defined in your BeanProvider.

[Inject( source="userService" )]
public var service:RemoteObject;

...

// will inject this from BeanProvider
<mx:RemoteObject id="userService" />

Inject bean property

Swiz can also inject public bean properties, rather than just the beans themselves using dot notation. In the following example "userModel" is the name of a bean, and we are injecting its currentUser property.

[Inject( source="userModel.currentUser" )]
public var currentUser : User;

If the bean property is bindable and the decorated property is public, you can have Swiz create a binding to the source property by adding bind="true" to the [Inject] tag:

[Inject( source="userModel.currentUser", bind="true" )]
public var currentUser : User;

As of Swiz 1.3, you can also inject nested properties, such as:

[Inject( source="userModel.currentUser.firstName" )]
public var firstName : String;

Two way bindings

To set up a reverse binding, so the bean property will receive updates made to the injection target, you can set the twoWay attribute of the [Inject] tag to true. This of course requires that the injection target is bindable as well.

[Bindable]
[Inject( source="userModel.currentUser", twoWay="true" )]
public var currentUser:User;

Setter injection

Swiz can also inject values into single argument methods. All of the attributes and policies mentioned above apply to setter injection as well, with the exception of twoWay.

[Inject]
public function setModel( model:UserModel ):void
{
    this.model = model;
}

Injection destination

Sometimes it's useful to define an injection someplace other than directly on a property/method. This is especially true in MXML views, where decorating a child component's property is not possible. Rather than creating a local variable and binding your component property to it, you can simply use the destination attribute of [Inject]. If this were defined in an MXML file, it would be wrapped in a Metadata tag.

[Inject( source="userModel.currentMode", destination="modeViewStack.selectedIndex" )]