170609 (금) - DI with Dagger2

DI with Dagger2

http://frogermcs.github.io/dependency-injection-with-dagger-2-the-api/

- source trace가 된다는 점이 Dagger2의 가장 큰 장점

- less dynamic 하면서 사용자가 hand-written code 한것과 비슷한 level 로 코드를 생성한다.

- Dagger2 API
    

public @interface Compnent {

Class<?>[] modules() default {};

Class<?>[] dependencies() default {};

}

public @interface Subcomponent {

Class<?>[] modules() default {};

}

public @interface Module {

Class<?>[] includes() default {};

}

public @interface Provides {}

public @interface MapKey {

boolean unwrapValue() default true;

}

public interface Lazy<T> {

T get();

}

- JSR-330 (Standard for DI in Java)

public @interface Inject {}

public @interface Scope {}

public @interface Qualifier {}

- @Inject

- JSR-330 standard

- 3 difference ways to provide dependencies

- constructor

- 둘 이상의 생성자에 @Inject 하지는 못한다.

public class LoginActivityPresenter {
    
    private LoginActivity loginActivity;
    private UserDataStore userDataStore;
    private UserManager userManager;
    
    @Inject
    public LoginActivityPresenter(LoginActivity loginActivity,
                                  UserDataStore userDataStore,
                                  UserManager userManager) {
        this.loginActivity = loginActivity;
        this.userDataStore = userDataStore;
        this.userManager = userManager;
    }
}

- Field

- private 사용 불가능

public class SplashActivity extends AppCompatActivity {
    
    @Inject
    LoginActivityPresenter presenter;
    @Inject
    AnalyticsManager analyticsManager;
    
    @Override
    protected void onCreate(Bundle bundle) {
        super.onCreate(bundle);
        getAppComponent().inject(this);
    }
}

- Method

public class LoginActivityPresenter {
    
    private LoginActivity loginActivity;
    
    @Inject 
    public LoginActivityPresenter(LoginActivity loginActivity) {
        this.loginActivity = loginActivity;
    }

    @Inject
    public void enableWatches(Watches watches) {
        watches.register(this);    //Watches instance required fully constructed LoginActivityPresenter
    }
}

- @Module

- Dagger2 API

- 필요한  object가 생성되는 위치를 알 수 있다.

@Module
public class GithubApiModule {
    
    @Provides
    @Singleton
    OkHttpClient provideOkHttpClient() {
        OkHttpClient okHttpClient = new OkHttpClient();
        okHttpClient.setConnectTimeout(60 * 1000, TimeUnit.MILLISECONDS);
        okHttpClient.setReadTimeout(60 * 1000, TimeUnit.MILLISECONDS);
        return okHttpClient;
    }

    @Provides
    @Singleton
    RestAdapter provideRestAdapter(Application application, OkHttpClient okHttpClient) {
        RestAdapter.Builder builder = new RestAdapter.Builder();
        builder.setClient(new OkClient(okHttpClient))
               .setEndpoint(application.getString(R.string.endpoint));
        return builder.build();
    }
}

- @Provides

- return dependencies

- @Component

- build interface which wires everything together.

- @Module과 @Inject의 브릿지 역할

- @Component는 다른 compenent를 depend 가능

@Singleton
@Component(modules = {AppModule.class, GithubApiModule.class})
public interface AppComponent {

    void inject(GithubClientApplication githubClientApplication);

    Application getApplication();

    AnalyticsManager getAnalyticsManager();

    UserManager getUserManager();
}

@ActivityScope
@Component(modules = SplashActivityModule.class, dependencies = AppComponent.class)
public interface SplashActivityComponent {
    SplashActivity inject(SplashActivity splashActivity);

    SplashActivityPresenter presenter();
}

- @Scope

- JSR-330 standard

- custom scope annotation define

- validation process에 사용되어 가능한 빨리 그래프 구조 문제를 catch하는데 도움이 된다.

- object의 single instance를 유지

@Scope
public @interface ActivityScope {
}

- @MapKey

- dependencies collection

- String and Enums 만 지원

@MapKey(unwrapValue = true)
@interface TestKey {
    String value();
}

@Provides(type = Type.MAP)
@TestKey("foo")
String provideFooKey() {
    return "foo value";
}

@Provides(type = Type.MAP)
@TestKey("bar")
String provideBarKey() {
    return "bar value";
}

@Inject
Map<String, String> map;

map.toString() // => „{foo=foo value, bar=bar value}”

@Qualifier

- 동일한 interface를 가진 dependencies 에 대해 "tag"를 생성

@Provides
@Singleton
@GithubRestAdapter  //Qualifier
RestAdapter provideRestAdapter() {
    return new RestAdapter.Builder()
        .setEndpoint("https://api.github.com")
        .build();
}

@Provides
@Singleton
@FacebookRestAdapter  //Qualifier
RestAdapter provideRestAdapter() {
    return new RestAdapter.Builder()
        .setEndpoint("https://api.facebook.com")
        .build();
}

@Inject
@GithubRestAdapter
RestAdapter githubRestAdapter;

@Inject
@FacebookRestAdapter
RestAdapter facebookRestAdapter;