Dagger2で生成されるソースを読むと怖くない

読むと怖くないDagger2
kyobashi.dex #1

プロフィール
釘宮愼之介 / @kgmyshin
Androidエンジニア
福岡県福岡市南区野多目出身

この資料の目的
Dagger2で生成されるソースを読んで、
動きを理解する

今回話さないこと
•DIとは
•Dagger2の使い所
•どういう構成にするか
•DaggerとDagger2の違い

今回話すこと
ひたすら生成されたソースを見て
裏でどういう動きをするのかを見る

Target Annotation
•Component
•Module
•Singleton
•Inject
•Scope

Target Annotation
•Component
•Module
•Singleton
•Inject
•Scope 時間的に無理でした

public interface Bread { 
}
public class Chokokorone implements Bread { 
}

@Component(modules = BreadModule.class) 
interface BreadShop { 
Bread bread(); 
}
@Module 
public class BreadModule { 
@Provides 
Bread provideBread() { 
return new Chokokorone(); 
} 
}

BreadShop shop = DaggerBreadShop 
.builder() 
.breadModule(new BreadModule()) 
.build();
Bread bread = shop.bread();

.builder() 
.build();
Bread bread = shop.bread(); // Chokokorone

Generated Codes
• DaggerBreadShop
• BreadModule_ProvideBreadFactory

@Generated("dagger.internal.codegen.ComponentProcessor") 
public final class DaggerBreadShop implements BreadShop { 
private Provider<Bread> provideBreadProvider; 
 
private DaggerBreadShop(Builder builder) {  
assert builder != null; 
initialize(builder); 
} 
 
public static Builder builder() {  
return new Builder(); 
} 
 
public static BreadShop create() {  
return builder().build(); 
} 
 
private void initialize(final Builder builder) {  
this.provideBreadProvider = BreadModule_ProvideBreadFactory.create(builder.breadModule); 
} 
 
@Override 
public Bread bread() {  
return provideBreadProvider.get(); 
} 
 
public static final class Builder { 
private BreadModule breadModule; 
 
private Builder() {  
} 
 
public BreadShop build() {  
if (breadModule == null) { 
this.breadModule = new BreadModule(); 
} 
return new DaggerBreadShop(this); 
} 
 
public Builder breadModule(BreadModule breadModule) {  
throw new NullPointerException("breadModule"); 
} 
this.breadModule = breadModule; 
return this; 
} 
} 
}

} 
 
 
private Builder() {  
} 
 
public BreadShop build() {  
this.breadModule = new BreadModule(); 
} 
return new DaggerBreadShop(this); 
} 
 
public Builder breadModule(BreadModule breadModule) {  
throw new NullPointerException("breadModule"); 
} 
this.breadModule = breadModule; 
return this; 
} 
}

public final class DaggerBreadShop implements BreadShop { 
private Provider<Bread> provideBreadProvider; 
 
private DaggerBreadShop(Builder builder) {  
assert builder != null; 
initialize(builder); 
} 
 
this.provideBreadProvider =
BreadModule_ProvideBreadFactory.create(builder.breadModule); 
} 
 
@Override 
} 
 
 
private Builder() {

public final class BreadModule_ProvideBreadFactory implements Factory<Bread> { 
private final BreadModule module; 
 
public BreadModule_ProvideBreadFactory(BreadModule module) {  
assert module != null; 
this.module = module; 
} 
 
@Override 
public Bread get() {  
Bread provided = module.provideBread(); 
if (provided == null) { 
throw new NullPointerException("Cannot return null from a non-@Nullable @Provides m
} 
return provided; 
} 
 
public static Factory<Bread> create(BreadModule module) {  
return new BreadModule_ProvideBreadFactory(module); 
} 
}

DaggerBreadShop::bread()
BreadModule_ProvideBreadFactory::get()

BreadModule::provideBread()

new Chokokorone()!!

Bread bread(); 
}
@Module 
public class BreadModule { 
@Provides 
} 
}
Before

@Singleton
Bread bread(); 
}
@Module 
public class BreadModule {
@Singleton 
@Provides 
} 
}
After

}
Before

this.provideBreadProvider =  
ScopedProvider.create( 
BreadModule_ProvideBreadFactory.create(builder.breadModule) 
); 
}
After

public final class ScopedProvider<T> implements Provider<T> {
 
:
 
@Override 
public T get() { 
// double-check idiom from EJ2: Item 71 
Object result = instance; 
if (result == UNINITIALIZED) { 
synchronized (this) { 
result = instance; 
if (result == UNINITIALIZED) { 
instance = result = factory.get(); 
} 
} 
} 
return (T) result; 
}
 
:
 
}

ScopedProvider::get()

new Chokokorone()!! (1度取得したら使い回す)

Bread bread(); 
}
Before

.builder() 
.build();
Bread bread = shop.bread();
Before

void bread(Lunch lunch); 
}
After
public class Lunch { 
@Inject 
Bread bread; 
}

.builder() 
.build(); 
Lunch lunch = new Lunch(); 
shop.bread(lunch); // lunch.bread is Chokokorone
After

Generated Codes
• DaggerBreadShop
• BreadModule_ProvideBreadFactory
• Lunch_MembersInjector

} 
 
@Override 
}
Before

this.lunchMembersInjector =
Lunch_MembersInjector.create(provideBreadProvider); 
} 
 
@Override 
public void bread(Lunch lunch) {  
lunchMembersInjector.injectMembers(lunch); 
}
After

public final class Lunch_MembersInjector implements MembersInjector<Lunch> { 
private final Provider<Bread> breadProvider; 
 
public Lunch_MembersInjector(Provider<Bread> breadProvider) {  
assert breadProvider != null; 
this.breadProvider = breadProvider; 
} 
 
@Override 
public void injectMembers(Lunch instance) {  
if (instance == null) { 
throw new NullPointerException("Cannot inject members into a null reference
} 
instance.bread = breadProvider.get(); 
} 
 
public static MembersInjector<Lunch> create(Provider<Bread> breadProvider) {  
return new Lunch_MembersInjector(breadProvider); 
} 
}

DaggerBreadShop::bread(Lunch launch)

Lunch_MembersInjector::injectMembers(Lunch launch)

lunch = BreadModule_ProvideBreadFactory::get()

lunch = BreadModule::provideBread()

lunch = BreadModule::provideBread()
lunch = new Chokokorone()!!

まとめ
Dagger2は怖くない

Dagger2で生成されるソースを読むと怖くない

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