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layout: docpage title: IoC Container description: Crux IoC Container permalink: /libraries/crux/ioc-container

Crux IoC Container

Inversion of Control in Crux

Page Contents:

• The BeanProvider Class
• Prototype Beans
• Externalizing Configuration Values

The BeanProvider Class

The IoC (Inversion of control) container of Crux is the BeanProvider class. In the BeanProvider you typically define non-view classes that you want registered with the framework and available as injec

<?xml version="1.0" encoding="utf-8"?>
<crux:BeanProvider
    xmlns:crux="library://ns.apache.org/royale/crux"
    xmlns:model="com.example.model.*"
    xmlns:control="com.example.control.*">

    <model:ApplicationModel id="applicationModel"/>
    <control:UserController id="userController"/>

</crux:BeanProvider>

Most applications define at least one Beans.mxml in the root package and pass it to the Crux tag‘s beanProviders property in the application’s main MXML file. For clarity and simplicity, it is recommended that you define your beans in a separate file, using BeanProvider as the root tag, as shown above. However, if for some reason you choose to define your beans inline in the Crux tag, you’ll need to wrap your objects with the Bean tag to ensure they are processed correctly:

<crux:Crux>
    <crux:beanProviders>
        <crux:BeanProvider>
            <crux:Bean name="applicationModel">
                <model:ApplicationModel/>
            </crux:Bean>
            <crux:Bean name="userController">
                <control:UserController/>
            </crux:Bean> 
        </crux:BeanProvider>
    </crux:beanProviders>

    <crux:config>
        <crux:SwizConfig
            eventPackages="com.foo.events, org.bar.events"
            viewPackages="com.foo.views, org.bar.events"/>
    </crux:config>
</crux:Crux>

Prototype Beans

Similar to Spring’s prototype scope{:target=‘_blank’}, Crux provides a Prototype tag. Prototype enables a few different things:

• Constructor injection – you can pass up to 8 arguments to your bean’s constructor
• Unique copy for each injection target (like prototype scope behavior in Spring)
• Deferred instantiation – Prototype beans will not be created until they are needed for injection

<crux:Prototype id="editViewPresoModel"
    type="{ EditViewPresentationModel }"
    constructorArguments="{ someOtherBean }" />

If you want deferred instantiation and/or constructor injection but not a unique copy for each injection you can set Prototype’s singleton property to true.

A Prototype bean created and injected into a view is not destroyed when the view is removed. Crux cannot know what else you may have done with the Prototype. If you wish to tear down a Prototype bean when a view is removed, implement a [PreDestroy] method and dispatch a TEAR_DOWN_BEAN event for the Prototype bean.

Externalizing Configuration Values

Bean property values can also be defined in external XML files. The CruxConfigValueLoader Crux extension provides one way to handle this. For example, an XML file with this structure:

<config>
    <value1>This is value 1.</value1>
    <value2>This is value 2.</value2>
</config>

Can be loaded and used in a BeanProvider by doing:

<externalconfig:CruxConfigValueLoader id="configLoader" source="config.xml" />
<controller:MyController id="myController"
    value1="{configLoader.configData.config.value1}"
    value2="{configLoader.configData.config.value2}" />

The CruxConfigValueLoader can be injected just like any other bean:

[Inject]
public var configLoader : CruxConfigValueLoader;

Finally, you can create an event handler to execute after the external data is loaded (remember to add “org.apache.royale.crux.externalconfig.event” to your eventPackages):

[EventHandler( event = "ConfigLoaderEvent.CONFIG_LOAD_COMPLETE", properties = "configData" )]
public function onConfigLoadComplete( configData : Object ) : void
{
    // You can now reference the value with syntax such as:
    // configData.config.value1, configData.config.value2, etc.
}