Dagger-Android：缺少模块的setter

Question

DataModule:

@Module
class DataModule constructor(application: App){

    private var db : Database = Room.databaseBuilder(application.applicationContext,
            Database::class.java, "database.db")
            .build()

    @Provides
    @PerApplication
    fun provideDatabase(): Database {
        return db
    }

App:

class App : DaggerApplication() {

    @Inject lateinit var activityDispatchingAndroidInjector: DispatchingAndroidInjector<Activity>

    override fun onCreate() {
        super.onCreate()
        setupTimber()
       // setupCrashlytics()
        RxPaparazzo.register(this)
    }

    override fun applicationInjector(): AndroidInjector<out App> {
        return DaggerApplicationComponent.builder()
                .dataModule(DataModule(this)).create(this)
    }

ApplicationComponent:

@PerApplication
@Component(modules = [AndroidSupportInjectionModule::class, ActivityBindingModule::class, ApplicationModule::class, DataModule::class, ServiceModule::class])
interface ApplicationComponent : AndroidInjector<App> {
    @Component.Builder
    abstract class Builder : AndroidInjector.Builder<App>()

}

I get error:

Error:(21, 2) error: @Component.Builder is missing setters for required modules or components: [com.org.injection.module.DataModule]
    public static abstract class Builder extends dagger.android.AndroidInjector.Builder<com.org.App> {
                       ^

Answer 1

That happens, because you have declared, that DataModule needs an instance of application object in order to be constructed, but you have not specified how to create that module. If a @Module annotated class has not any parameters in its constructor (ie has a default constructor), then dagger will take of creating the module. Otherwise, you have to specify how to create the module manually.

Change the topmost (application) component to following:

    @Component(modules = [...])
    interface AppComponent {
      @Component.Builder
      interface Builder {
        // @BindsInstance will make `application` to be accessible in the graph
        @BindsInstance
        fun application(application: Application): Builder
        fun build(): AppComponent
      }
    }

Now change DataModule to ask for an instance of application object:

    @Module
    class DataModule {
      @Provides
      fun provideDatabase(application: Application): Database {
        return ...
      }
    }