Hello World example - suggestions?

[Thorbjørn Ravn Andersen]

I am getting acquainted with Dagger 2, and could not find a "Hello World" example, so I've written one (which might be adapted and added to the official documentation)

---

package demo;

import dagger.Component;
import dagger.Provides;
import dagger.Module;

import java.util.concurrent.Callable;

public class HelloWorld {
    public static void main(String[] args) throws Exception {
        System.out.println(DaggerHelloWorld_OurComponent.builder().build().getCallable().call());
    }

    @Component(modules = OurModule.class)
    interface OurComponent {
        Callable getCallable();
    }
}

@Module
class OurModule {
    @Provides
    Callable getHelloWorld() {
        return () -> "Hello World";
    }
}

---

I've used Callable to keep the class count down.  OurModule and OurComponent is to allow

the import statements.

Have I missed anything, or is this as tight as it can get?  

/Thorbjørn

[Jens]

While a hello world example should be short it should also be very concrete and understandable. IMHO your naming is too generic and binding Callable is kind of unrealistic so overall I would not like that as a hello world example.

You better create an interface called MessagePrinter and a class ConsoleMessagePrinterImpl that you can bind with dagger. In your main() method you can then do component.printer().print("Hello world"). This also allows you to choose concrete names for your component and module like HelloWorldComponent and ConsolePrinterModule.

-- J.

[Thorbjørn Ravn Andersen]

Duly noted.  Perhaps you would like to adapt it so we have a complete example as you would like it to be?

[Jens]

Duly noted.  Perhaps you would like to adapt it so we have a complete example as you would like it to be?

I guess the following would be my Hello World!

package com.example.dagger;

import dagger.Component;

import dagger.Module;

import dagger.Provides;

public class Example {

  interface Printer {

    void printMsg(String msg);

  }

  static class ConsolePrinter implements Printer {

    @Override

    public void printMsg(String msg) {

      System.out.println(msg);

    }

  }

  @Component(modules = ConsoleModule.class)

  interface HelloWorldApp {

    Printer getPrinter();

  }

  @Module

  static class ConsoleModule {

    @Provides

    Printer providePrinter() {

      return new ConsolePrinter();

    }

  }

  public static void main(String[] args) {

    HelloWorldApp app = DaggerExample_HelloWorldApp.create();

    app.getPrinter().printMsg("Hello World!");

  }

}

-- J. 

[Thorbjørn Ravn Andersen]

Thanks for the response.   Several revisions later the result is on https://github.com/ravn/dagger2-hello-world