ম্যানুয়াল নির্ভরতা ইনজেকশন

class UserRepository(     private val localDataSource: UserLocalDataSource,     private val remoteDataSource: UserRemoteDataSource ) { ... }  class UserLocalDataSource { ... } class UserRemoteDataSource(     private val loginService: LoginRetrofitService ) { ... }

class UserLocalDataSource {     public UserLocalDataSource() { }     ... }  class UserRemoteDataSource {      private final Retrofit retrofit;      public UserRemoteDataSource(Retrofit retrofit) {         this.retrofit = retrofit;     }      ... }  class UserRepository {      private final UserLocalDataSource userLocalDataSource;     private final UserRemoteDataSource userRemoteDataSource;      public UserRepository(UserLocalDataSource userLocalDataSource, UserRemoteDataSource userRemoteDataSource) {         this.userLocalDataSource = userLocalDataSource;         this.userRemoteDataSource = userRemoteDataSource;     }      ... }

class LoginActivity: Activity() {      private lateinit var loginViewModel: LoginViewModel      override fun onCreate(savedInstanceState: Bundle?) {         super.onCreate(savedInstanceState)          // In order to satisfy the dependencies of LoginViewModel, you have to also         // satisfy the dependencies of all of its dependencies recursively.         // First, create retrofit which is the dependency of UserRemoteDataSource         val retrofit = Retrofit.Builder()             .baseUrl("https://example.com")             .build()             .create(LoginService::class.java)          // Then, satisfy the dependencies of UserRepository         val remoteDataSource = UserRemoteDataSource(retrofit)         val localDataSource = UserLocalDataSource()          // Now you can create an instance of UserRepository that LoginViewModel needs         val userRepository = UserRepository(localDataSource, remoteDataSource)          // Lastly, create an instance of LoginViewModel with userRepository         loginViewModel = LoginViewModel(userRepository)     } }

public class MainActivity extends Activity {      private LoginViewModel loginViewModel;      @Override     protected void onCreate(Bundle savedInstanceState) {         super.onCreate(savedInstanceState);         setContentView(R.layout.activity_main);          // In order to satisfy the dependencies of LoginViewModel, you have to also         // satisfy the dependencies of all of its dependencies recursively.         // First, create retrofit which is the dependency of UserRemoteDataSource         Retrofit retrofit = new Retrofit.Builder()                 .baseUrl("https://example.com")                 .build()                 .create(LoginService.class);          // Then, satisfy the dependencies of UserRepository         UserRemoteDataSource remoteDataSource = new UserRemoteDataSource(retrofit);         UserLocalDataSource localDataSource = new UserLocalDataSource();          // Now you can create an instance of UserRepository that LoginViewModel needs         UserRepository userRepository = new UserRepository(localDataSource, remoteDataSource);          // Lastly, create an instance of LoginViewModel with userRepository         loginViewModel = new LoginViewModel(userRepository);     } }

// Container of objects shared across the whole app class AppContainer {      // Since you want to expose userRepository out of the container, you need to satisfy     // its dependencies as you did before     private val retrofit = Retrofit.Builder()                             .baseUrl("https://example.com")                             .build()                             .create(LoginService::class.java)      private val remoteDataSource = UserRemoteDataSource(retrofit)     private val localDataSource = UserLocalDataSource()      // userRepository is not private; it'll be exposed     val userRepository = UserRepository(localDataSource, remoteDataSource) }

// Container of objects shared across the whole app public class AppContainer {      // Since you want to expose userRepository out of the container, you need to satisfy     // its dependencies as you did before     private Retrofit retrofit = new Retrofit.Builder()             .baseUrl("https://example.com")             .build()             .create(LoginService.class);      private UserRemoteDataSource remoteDataSource = new UserRemoteDataSource(retrofit);     private UserLocalDataSource localDataSource = new UserLocalDataSource();      // userRepository is not private; it'll be exposed     public UserRepository userRepository = new UserRepository(localDataSource, remoteDataSource); }

// Custom Application class that needs to be specified // in the AndroidManifest.xml file class MyApplication : Application() {      // Instance of AppContainer that will be used by all the Activities of the app     val appContainer = AppContainer() }

// Custom Application class that needs to be specified // in the AndroidManifest.xml file public class MyApplication extends Application {      // Instance of AppContainer that will be used by all the Activities of the app     public AppContainer appContainer = new AppContainer(); }

class LoginActivity: Activity() {      private lateinit var loginViewModel: LoginViewModel      override fun onCreate(savedInstanceState: Bundle?) {         super.onCreate(savedInstanceState)          // Gets userRepository from the instance of AppContainer in Application         val appContainer = (application as MyApplication).appContainer         loginViewModel = LoginViewModel(appContainer.userRepository)     } }

public class MainActivity extends Activity {      private LoginViewModel loginViewModel;      @Override     protected void onCreate(Bundle savedInstanceState) {         super.onCreate(savedInstanceState);         setContentView(R.layout.activity_main);          // Gets userRepository from the instance of AppContainer in Application         AppContainer appContainer = ((MyApplication) getApplication()).appContainer;         loginViewModel = new LoginViewModel(appContainer.userRepository);     } }

// Definition of a Factory interface with a function to create objects of a type interface Factory<T> {     fun create(): T }  // Factory for LoginViewModel. // Since LoginViewModel depends on UserRepository, in order to create instances of // LoginViewModel, you need an instance of UserRepository that you pass as a parameter. class LoginViewModelFactory(private val userRepository: UserRepository) : Factory {     override fun create(): LoginViewModel {         return LoginViewModel(userRepository)     } }

// Definition of a Factory interface with a function to create objects of a type public interface Factory<T> {     T create(); }  // Factory for LoginViewModel. // Since LoginViewModel depends on UserRepository, in order to create instances of // LoginViewModel, you need an instance of UserRepository that you pass as a parameter. class LoginViewModelFactory implements Factory {      private final UserRepository userRepository;      public LoginViewModelFactory(UserRepository userRepository) {         this.userRepository = userRepository;     }      @Override     public LoginViewModel create() {         return new LoginViewModel(userRepository);     } }

// AppContainer can now provide instances of LoginViewModel with LoginViewModelFactory class AppContainer {     ...     val userRepository = UserRepository(localDataSource, remoteDataSource)      val loginViewModelFactory = LoginViewModelFactory(userRepository) }  class LoginActivity: Activity() {      private lateinit var loginViewModel: LoginViewModel      override fun onCreate(savedInstanceState: Bundle?) {         super.onCreate(savedInstanceState)          // Gets LoginViewModelFactory from the application instance of AppContainer         // to create a new LoginViewModel instance         val appContainer = (application as MyApplication).appContainer         loginViewModel = appContainer.loginViewModelFactory.create()     } }

// AppContainer can now provide instances of LoginViewModel with LoginViewModelFactory public class AppContainer {     ...      public UserRepository userRepository = new UserRepository(localDataSource, remoteDataSource);      public LoginViewModelFactory loginViewModelFactory = new LoginViewModelFactory(userRepository); }  public class MainActivity extends Activity {      private LoginViewModel loginViewModel;      @Override     protected void onCreate(Bundle savedInstanceState) {         super.onCreate(savedInstanceState);         setContentView(R.layout.activity_main);          // Gets LoginViewModelFactory from the application instance of AppContainer         // to create a new LoginViewModel instance         AppContainer appContainer = ((MyApplication) getApplication()).appContainer;         loginViewModel = appContainer.loginViewModelFactory.create();     } }

class LoginContainer(val userRepository: UserRepository) {      val loginData = LoginUserData()      val loginViewModelFactory = LoginViewModelFactory(userRepository) }  // AppContainer contains LoginContainer now class AppContainer {     ...     val userRepository = UserRepository(localDataSource, remoteDataSource)      // LoginContainer will be null when the user is NOT in the login flow     var loginContainer: LoginContainer? = null }

// Container with Login-specific dependencies class LoginContainer {      private final UserRepository userRepository;      public LoginContainer(UserRepository userRepository) {         this.userRepository = userRepository;         loginViewModelFactory = new LoginViewModelFactory(userRepository);     }      public LoginUserData loginData = new LoginUserData();      public LoginViewModelFactory loginViewModelFactory; }  // AppContainer contains LoginContainer now public class AppContainer {     ...     public UserRepository userRepository = new UserRepository(localDataSource, remoteDataSource);      // LoginContainer will be null when the user is NOT in the login flow     public LoginContainer loginContainer; }

class LoginActivity: Activity() {      private lateinit var loginViewModel: LoginViewModel     private lateinit var loginData: LoginUserData     private lateinit var appContainer: AppContainer       override fun onCreate(savedInstanceState: Bundle?) {         super.onCreate(savedInstanceState)         appContainer = (application as MyApplication).appContainer          // Login flow has started. Populate loginContainer in AppContainer         appContainer.loginContainer = LoginContainer(appContainer.userRepository)          loginViewModel = appContainer.loginContainer.loginViewModelFactory.create()         loginData = appContainer.loginContainer.loginData     }      override fun onDestroy() {         // Login flow is finishing         // Removing the instance of loginContainer in the AppContainer         appContainer.loginContainer = null         super.onDestroy()     } }

public class LoginActivity extends Activity {      private LoginViewModel loginViewModel;     private LoginData loginData;     private AppContainer appContainer;      @Override     protected void onCreate(Bundle savedInstanceState) {         super.onCreate(savedInstanceState);         setContentView(R.layout.activity_main);          appContainer = ((MyApplication) getApplication()).appContainer;          // Login flow has started. Populate loginContainer in AppContainer         appContainer.loginContainer = new LoginContainer(appContainer.userRepository);          loginViewModel = appContainer.loginContainer.loginViewModelFactory.create();         loginData = appContainer.loginContainer.loginData;     }      @Override     protected void onDestroy() {         // Login flow is finishing         // Removing the instance of loginContainer in the AppContainer         appContainer.loginContainer = null;          super.onDestroy();     } }