使用 Kotlin 在 Dagger2 中进行多重绑定

Question

所以，我有这个问题，我想我明白发生了什么，但我不知道解决办法。注意：我是 Dagger 2 的新手...我来自 SpringBoot，它在那里很懒惰，所以请放轻松。

I have a module that provides three methods, the last method depends on the first two methods like below:

@Module
class CoreModule {

    @Provides
    @Named("appName")
    fun appName() : String{
        return "Uburu Store"
    }

    @Provides
    @Named("appVersion")
    fun appVersion() : String {
        return "0.0.1"
    }

    @Provides
    @Named("appInfo")
    fun appInfo(appName: String, appVersion: String) : String {
        return "$appName Version:: $appVersion"
    }
}

I'm getting an error that:

[Dagger/MissingBinding] java.lang.String cannot be provided without an @Inject constructor or an @Provides-annotated method.

My ApplicationComponent class:

@Component(modules = [(CoreModule::class), (AndroidSupportInjectionModule::class), (ActivityBuildersModule::class)])
interface ApplicationComponent : AndroidInjector<ApplicationClass> {

    fun inject(application: Application)

    @Component.Builder
    interface Builder {

        @BindsInstance
        fun application(application: Application?): Builder?

        fun build(): ApplicationComponent?
    }

}

My activity class:

class MainActivity : DaggerAppCompatActivity() {

    @Inject @Named("appInfo") lateinit var appInfo : String

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        Toast.makeText(this, appInfo, Toast.LENGTH_LONG).show()
    }
}

I managed to make it work if I don't use @Named annotation in any of the two dependencies i.e if I delete one of the Two provided dependencies from CoreModule, and remove the @Named annotation from the only dependency left, it will work fine like below:

    @Module
    class CoreModule {
    
        @Provides
        fun appName() : String{
            return "Uburu Store"
        }
    
        @Provides
        @Named("appInfo")
        fun appInfo(appName: String) : String {
            return "$appName Version:: $"
        }
    
    }
//This will work just fine, which made me realize that the @Named must be making it difficult for Dagger to understand something.

这种方法的问题是我不能没有@Named，因为它需要相同数据类型的多重绑定，例如：String。

My research so far made it known to me that I have to use @JvmSuppressWildcards somewhere but I'm not sure where.

Answer 1

Dagger 提供了基于图中 class 类型的依赖项，在您的 CoreModule 的第一个代码片段中，它无法向 appInfo(String, String) 方法提供依赖项，因为它无法确定属于哪种 String 类型在哪里。修复很简单；在模块中需要它们的方法中注释您已经使用 @Named 限定符提供的依赖项：

@Module
class CoreModule {

    @Provides
    @Named("appName")
    fun appName() : String{
        return "Uburu Store"
    }

    @Provides
    @Named("appVersion")
    fun appVersion() : String {
        return "0.0.1"
    }

    @Provides
    @Named("appInfo")
    fun appInfo(@Named("appName") appName: String, @Named("appVersion") appVersion: String) : String {
        return "$appName Version:: $appVersion"
    }
}

您的第二个示例有效，因为图表中只提供了一种字符串类型。

有关详细信息，请转到 documentation 并滚动至限定符部分

使用 Kotlin 在 Dagger2 中进行多重绑定

Multi Binding In Dagger2 with Kotlin

android

kotlin

dagger-2