Dagger does not initialize Lazy lazy Variable?

Question

I am using Java and Dagger dependency injection framework. Often I have situations where I have to init a class but used later e.g.:

private final Message message;

public SomePresenter() {
  message = DaggerComponent.getMessage();
}

public someFuncA() {
  message.doSomething();
}

public someFuncB() {
  message.doSomething();
}

I want that message is initialized the first time it is requested and from that moment alway use the same message instance in this class. How can I do that?

Edit:

I tried to use Lazy as follows but lazyMessage is undefined:

public class StartPresenter {

  @Inject
  Lazy<Message> lazyMessage; 

  @Inject
  public StartPresenter(ConfigObject config) {
  }

}

Here is my dagger2 configuration:

@Component(modules = {ApplicationModule.class})
@Singleton
public interface ApplicationComponent {

   Message getMessage();
}

@Module()
public class CoreModule {

  @Provides @Singleton
  Message provideMessage() {
    return new MessageImpl();
  }  
}

How do I get lazyMessage being instantiated by dagger?

access the `message` only via getter where you will initialize it — NeplatnyUdaj, Mar 20 '15 at 14:49

score 3 · Accepted Answer · edited Mar 20 '15 at 15:38

3

Use the Lazy class like

@Inject Lazy<Message> message;

In your code use:

//Doing something with message
message.get().messageMethod();

Here's the documentation for Lazy

Dagger will only wire up the class when get() is called. It will return the same instance everytime get() is called.

edited Mar 20 '15 at 15:38

Michael

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answered Mar 20 '15 at 14:50

yxre

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How do you create an instance of StartPresenter? – Vlad Kuts Mar 20 '15 at 21:54
Can we use Lazy in constructor injection in dagger? – Astha Garg Nov 16 '21 at 07:23

Dagger does not initialize Lazy lazy Variable?

1 Answers1