Android-开发笔记-Kodein

Kodein(Kotlin Dependency Injection)并不是一个整整的依赖注入框架，而是依赖检索容器。

Kodein作用

• Lazily instantiate your dependencies when needed
• Stop caring about dependency initialization order
• Easily bind classes or interfaces to their instance or provider
• Easily debug your dependency bindings and recursions
• It proposes a very simple and readable declarative DSL

如何使用？

1.Install

compile 'org.kodein.di:kodein-di-generic-jvm:5.2.0'
compile 'org.kodein.di:kodein-di-framework-android-x:5.2.0'

2.Declare the dependency bindings in the Android Application, having it implements KodeinAware

class MyApp : Application(), KodeinAware {
	override val kodein = Kodein.lazy {
	    /* bindings */
	}
}

3.Retrieve the Kodein object with the colsestKodein function

class MyActivity : Activity(), KodeinAware {
    override val kodein by closestKodein()
    val ds: DataSource by instance()
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        ds.connect()
        /* ... */
    }
}

绑定方式

1.Singleton 单例 传入 () → T

2.Provider 每次加载都生成新的实例，无参， 传入() -> T

val kodein = Kodein {
    bind<Die>() with provider { RandomDie(6) }
}

3.Factory 跟Provider相似，每次调用会返回一个新的实例，不同的是接受以定义类型的参数并返回绑定类型的对象 (A) -> T

val kodein = Kodein {
    bind<Die>() with factory { sides: Int -> RandomDie(sides) }
}