DaggerMock library -how does it override module? - android

The DaggerMock library, is used to override dagger modules with fake implementation. Lets take a look at one robolectric topic that is confusing me:
#RunWith(RobolectricGradleTestRunner.class)
#Config(constants = BuildConfig.class, sdk = 21)
public class MainActivityTest {
#Rule public final DaggerMockRule<MyComponent> mockitoRule = new DaggerMockRule<>(MyComponent.class, new MyModule())
.set(new DaggerMockRule.ComponentSetter<MyComponent>() {
#Override public void setComponent(MyComponent component) {
((App) RuntimeEnvironment.application).setComponent(component);
}
});
#Mock RestService restService;
#Mock MyPrinter myPrinter;
#Test
public void testCreateActivity() {
when(restService.doSomething()).thenReturn("abc");
Robolectric.setupActivity(MainActivity.class);
verify(myPrinter).print("ABC");
}
}
So i want to know, with this Rule what exactly is happening ? I can see that RestService was being provided by MyModule but is now being replaced with a mock. But in the examples i don't see a #Inject anywhere so i'm confused how the module was even used in the first place to provide any dependencies ?

I am the author of DaggerMock, thanks for trying it!
The implementation is a bit complicated, the rule create a dynamic subclass of the module (using mockito) and override the provides methods. The rule scans the test fields so it return a field when the module has a method that returns the same type.
The final result is very similar to Mockito InjectMocks annotation. You can take a look at the implementation on github, the core class that override the module is this: https://github.com/fabioCollini/DaggerMock/blob/master/lib/src/main/java/it/cosenonjaviste/daggermock/MockOverrider.java
I release this lib just a week ago, any feedback is welcome!

Related

Dagger2 dependency injection: How does it work in an android app?

I am trying to understand an example for an app with offline support using retrofit and room:
You can find the code for it here:
This project is using dependency injections with Dagger2. I've never worked with it so I am trying to understand how things work together. I understand the purpose of dependency injection but I don't understand the implementation of the project above.
I found a very good introduction into Dagger2 here:
A Friendly Introduction to Dagger 2
Dagger 2 example Code:
I worked through it and got most of it. Back to the actual project I am trying to understand (link 2). It still doesn't make sense to me and here is why:
The interface AppComponent has one method which is used:
public void inject(MainActivity2ViewModel viewModelModule); The return type is void. In the Dagger2 sample project (link 3 and 4) they use WeatherReporter getWeatherReporter(); which makes sense because later they call this method to get a WeatherReporter-Instance and Dagger2 manages all of the instantation process in the background. But I get nothing if the return type is void. Why is the return type not an object?
There is one #Inject in MainActivity2ViewModel:
#Inject
public void setRepository(GitHubRepository2 repository) {
this.repository = repository;
}
repository is the only field of MainActivity2ViewModel so it is a dependency. The GitHubRepository2 constructor has 3 parameters:
#Inject
public GitHubRepository2(GitHubApi api, GitHubDao dao, Executor executor)
For each of them there is a module explaining how to create those objects. But why is there an AppModule and a NetModule? Maybe the AppModule is there because DaoModule needs an Application reference but why is there a NetModule and where is it used?
There's a lot of comprehensive tutorials about Dagger2 in Android. But I'll show you a glimpse of what it's used for. And minimal usage.
Ultimately, dagger will use the annotation #Inject which will provide(reference to the object or value) to the variable.
Injection is usually used on reusable or boilerplate objects like Dao, Repository, ViewModel, NetworkAdapter
class SomethingThatRequiresNetwork { // Activity, Fragment
#Inject
MyReusableNetworkAdapter myReusableNetworkAdapter;
String baseUrl; // for example purpose only
SomeDependency someDependency;
void init() {
// #NOTE: DaggerMyExampleComponent is a generated class. It will be red before compilation.
MyExampleComponent MyExampleComponent = DaggerMyExampleComponent.builder().build();
MyExampleComponent.inject(this); // the actual injection happens here
}
// yes, you can just use #Inject on the variables directly but this is another use.
#Inject
void methodInjection(String baseUrl, SomeDependency someDependency) {
this.baseUrl = baseUrl;
this.someDependency = someDependency;
}
}
// ANSWER to the two questions
// this is a pseudocode of the generated code. You do not write this
// MyExampleComponent class
void inject(SomethingThatRequiresNetwork obj) {
// #NOTE: modules are actually instantiated by MyExampleComponent. Not called statically. I just shortened it
obj.myReusableNetworkAdapter = NetModule.provideNetworkAdapter();
obj.methodInjection(NetModule.provideBaseUrl(), SomeModule.provideSomeDependency());
}
// these here are modules that provide by return TYPE
// you write these
#Module
class NetModule {
#Provides
#Singleton
String provideBaseUrl() {
return "www.some-url.com";
}
#Provides
#Singleton // will store the object and reuse it.
// #NOTE: provision can work internally within modules or inter-module. the input here is provided by provideBaseUrl
MyReusableNetworkAdapter provideNetworkAdapter(String baseUrl) {
return new MyReusableNetworkAdapter(baseUrl);
}
}
#Modules
class SomeModule {
#Provides
#Singleton
SomeDependency provideSomeDependency() {
return new SomeDependency();
}
}
// Component. uses modules
#Singleton // .build() will reuse
#Component(modules = {NetModule.class, SomeModule.class})
interface MyExampleComponent {
// the method name doesn't matter
// the class type does matter though.
void inject(SomethingThatRequiresNetwork somethingThatRequiresNetwork);
// some other class that needs injection. #NOTE: I did not give example for this
void inject(SomethingThatRequiresDependency some);
}
NOTE. This code is usually written from bottom to top lol. You start writing the Component then Module then Injections.
Just follow the calls from the top of this answer and you'll figure out how Dagger2 works.

Dagger 2.2 component builder module method deprecated

I started using dagger 2.2 and the module methods in the Component builder are deprecated.
This is my Application component :
#Component(modules = ApplicationModule.class)
public interface ApplicationComponent {
void inject(Application application);
}
And the Application module:
#Module
public class ApplicationModule {
Application application;
public ApplicationModule(Application application) {
this.application = application;
}
#Provides
#Singleton
Application providesApplication() {
return application;
}
}
Here is the generated class:
#Generated(
value = "dagger.internal.codegen.ComponentProcessor",
comments = "https://google.github.io/dagger"
)
public final class DaggerApplicationComponent implements ApplicationComponent {
private DaggerApplicationComponent(Builder builder) {
assert builder != null;
}
public static Builder builder() {
return new Builder();
}
public static ApplicationComponent create() {
return builder().build();
}
#Override
public void inject(Application application) {
MembersInjectors.<Application>noOp().injectMembers(application);
}
public static final class Builder {
private Builder() {}
public ApplicationComponent build() {
return new DaggerApplicationComponent(this);
}
/**
* #deprecated This module is declared, but an instance is not used in the component. This method is a no-op. For more, see https://google.github.io/dagger/unused-modules.
*/
#Deprecated
public Builder applicationModule(ApplicationModule applicationModule) {
Preconditions.checkNotNull(applicationModule);
return this;
}
}
}
How do I initialize the component if not with the ComponentBuilder?
You should read the description of why it is deprecated. If you are using an IDE like IntelliJ or Android Studio you can just select the method and hit Control + Q on Windows to read the Javadoc including the deprecation notice.
The Javadoc reads:
#deprecated This module is declared, but an instance is not used in the component. This method is a no-op. For more, see https://google.github.io/dagger/unused-modules.
And from this link you can see:
When the Dagger processor generates components, it only requires instances of modules and component dependencies that are explicitly needed to supply requests for a binding.
If all of a module’s methods that are used in the component are static, Dagger does not need an instance of that module at all. Dagger can invoke the static methods directly without a module.
If a module provides no bindings for a Component, no instance of that module is necessary to construct the graph.
It is safe to say that you can just ignore the deprecation. It is intended to notify you of unused methods and modules. As soon as you actually require / use Application somewhere in your subgraph the module is going to be needed, and the deprecation warning will go away.
It show deprecated because you are not using Component and module in your application by
#Inject
SomeObjectFromModule mSomeObject
if you are not injecting dependencies in your applications there is no use of initialising your component so dagger look for at least one usage
once you add these lines in any classes you want to inject views and then clean build and rebuild the project and your deprecation will be solved
It showing error when my Module have no #Provides method or the object that provide by Dagger is not used in app.
Example to remove deprecated module
Module
#Module
public class SecondActivityModule {
#Provides
Book provideBookTest() {
return new Book();
}
}
Activity
public class SecondActivity extends AppCompatActivity {
#Inject
Book test;
...
}
OR in Component
#Component(modules = SecondModule.class)
public interface SecondComponent {
void inject(SecondActivity activity);
Book getBookTest();
}
I have the same problem with host and I just want everyone has deprecated issue on Generated component builder class should check two things to save time:
1/ Correct dagger syntax for module, component also check carefully where you inject.
2/ Must have injection object (inject annotation and its object) in place you want to inject or else the dagger compiler cannot see where to use your module so some method will be deprecated.Just inject at least one module's provides to your injection place and re-compile the code, you won't have that issue anymore :)
you will get module method deprecated if you declare void inject(AppCompactActivity activity); in component class. instead of you have to use tight coupling like following void inject(MainActivity activity);and rebuild your project you will see, there is no deprecate method in module class

Android Tests: use Dagger2 + Gradle

I understand how Dagger2 works,
I understand it allows to easily swap dependencies, so we can use mocks for testing.
Point is that I am not sure I understand how am I supposed to provide different Dagger2 Components implementations for testing and for debug/production.
Would I need to create 2 Gradle productFlavors (e.g "Production"/"Test")
that would contain 2 different Components definition?
Or can I specify that I want to use the mock Component for test compile and the non mock Component for non test builds?
I am confused, please some clarification would be great!
Thanks a lot!
Unit testing
Don’t use Dagger for unit testing
For testing a class with #Inject annotated constructor you don't need dagger. Instead create an instance using the constructor with fake or mock dependencies.
final class ThingDoer {
private final ThingGetter getter;
private final ThingPutter putter;
#Inject ThingDoer(ThingGetter getter, ThingPutter putter) {
this.getter = getter;
this.putter = putter;
}
String doTheThing(int howManyTimes) { /* … */ }
}
public class ThingDoerTest {
#Test
public void testDoTheThing() {
ThingDoer doer = new ThingDoer(fakeGetter, fakePutter);
assertEquals("done", doer.doTheThing(5));
}
}
Functional/integration/end-to-end testing
Functional/integration/end-to-end tests typically use the production
application, but substitute fakes[^fakes-not-mocks] for persistence,
backends, and auth systems, leaving the rest of the application to
operate normally. That approach lends itself to having one (or maybe a
small finite number) of test configurations, where the test
configuration replaces some of the bindings in the prod configuration.
You have two options here:
Option 1: Override bindings by subclassing modules
#Component(modules = {AuthModule.class, /* … */})
interface MyApplicationComponent { /* … */ }
#Module
class AuthModule {
#Provides AuthManager authManager(AuthManagerImpl impl) {
return impl;
}
}
class FakeAuthModule extends AuthModule {
#Override
AuthManager authManager(AuthManagerImpl impl) {
return new FakeAuthManager();
}
}
MyApplicationComponent testingComponent = DaggerMyApplicationComponent.builder()
.authModule(new FakeAuthModule())
.build();
Option 2: Separate component configurations
#Component(modules = {
OAuthModule.class, // real auth
FooServiceModule.class, // real backend
OtherApplicationModule.class,
/* … */ })
interface ProductionComponent {
Server server();
}
#Component(modules = {
FakeAuthModule.class, // fake auth
FakeFooServiceModule.class, // fake backend
OtherApplicationModule.class,
/* … */})
interface TestComponent extends ProductionComponent {
FakeAuthManager fakeAuthManager();
FakeFooService fakeFooService();
}
More about it in the official documentation testing page.

how can I inject a dependency in a method?

I'm a beginner with dependency injection.. specifically Dagger 2. I'm trying to figure out if/how I can do something like this:
#Inject
public void someMethodName(int someInteger, SomeObject dependency){
// do something with the dependency.
}
Or do I need to put that dependency in as a class var? any help with this would be greatly appreciated. also in this case the variable someInteger is not a dependency, but is being added by the caller... does that matter?
can I call it like this:
this.someMethodName(5);
android studio does not like the above calling method (I'm assuming because I'm doing something wrong)
You need to create component which is annotated by #Component.
The Component accepts module which provides dependencies.
Every component's name that you create starts with Dagger prefix, e.g. for MyComponent.
Let's look at the following example:
#Singleton
#Component(modules = DemoApplicationModule.class)
public interface ApplicationComponent {
void inject(DemoApplication application);
}
We created ApplicationComponent with single injection method. What we're saying is that we want to inject certain dependencies in DemoApplication.
Moreover, in the #Component annotations we specify module with provision methods.
This is like our module looks like:
#Module
public class DemoApplicationModule {
private final Application application;
public DemoApplicationModule(Application application) {
this.application = application;
}
#Provides #Singleton SomeIntegerHandler provideIntegerHandler() {
return new MySomeIntegerHandlerImpl();
}
}
What we're saying by creating DemoApplicationModule is that the module can provide desired dependencies in the injection place specified by our Component.
public class DemoApplication extends Application {
private ApplicationComponent applicationComponent;
#Inject SomeIntegerHandler handler;
#Override public void onCreate() {
super.onCreate();
applicationComponent = DaggerApplicationComponent.builder()
.demoApplicationModule(new DemoApplicationModule(this))
.build();
applicationComponent.inject(this);
handler.someMethodName(5);
}
}
See documentation what you kind of dependencies you can obtain. Additionally to obtaining just raw instance you can obtain Provider, Factory or Lazy instance.
http://google.github.io/dagger/api/latest/dagger/Component.html
You can also create scoped dependencis, the lifecycles of which depend on the lifecycle of injection places, like Activities or Fragments.
Hope I gave you the basic notion of what Dagger is.
YOU CAN USE SOME INTERFACE
public interface myDependence{
int myFunction(int value);
}
NOW IMPLEMENT IN YOU CLASS
public myClass implements MyDependence{
#Override
int myFunction(int value){
// do something
}
}

What does #Module means in dagger for android?

I have read many blogs but still i am not able to figure out #Module annotation functioning in dagger.
#Inject i got that it provides dependency injection at runtime. But what does #Module does.
since the object graph is also built on module.
For ex i.e i have this snippet of code from https://github.com/AndroidBootstrap/android-bootstrap.
#Module(
complete = false,
injects = {
BootstrapApplication.class,
BootstrapAuthenticatorActivity.class,
MainActivity.class,
BootstrapTimerActivity.class,
}
)
public class BootstrapModule {
}
so what does it basically does. since i am also trying to build one application using dagger as dependency injection for android.But since I am not able to get #Module concept clearly I am just stuck.
Can anyone please help me out with some basic example or concept. I think this will be helpful for all who is using dagger.
If you have a look to the docs for the annotation, a #Module annotated class defines a class that contributes to the dagger object graph. In the Spring framework for example, the equivalent would be the #Configuration anntotation. It defines a configuration point for your object graph, where you declare which objects you want to be available for injection and their scopes.
As a simple example, let's say we want a singleton object to be used by any Activity in the app. It has to be created in the module:
#dagger.Module(injects = {MyActivity.class})
public class Module {
#Provides
#Singleton
public MySinletonBean provideMySingleton() {
return new MySinletonBean();
}
}
This will create a MySingleton object which can be injected in MyActivity. This is a very basic example, but we can perform other actions in the graph there, like using dependencies in the constructors:
#dagger.Module(injects = {MyActivity.class})
public class Module {
private DependencyBean dependency = new DependencyBean();
#Provides
#Singleton
public MySinletonBean provideMySingleton() {
return new MySinletonBean(dependency);
}
#Provides
#Singleton
public MySinletonBean provideMyOtherSingleton() {
return new MyOtherSinletonBean(dependency);
}
}
Then, in MyActivity we need to access the graph for the application in the onCreate method:
#Inject
MySingletonBean singleton;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.my_activity);
((MyApplication) getApplication()).getGraph().inject(this);
}
So, who does create the object graph here? The MyApplication class does it when your application starts (don't forger to add it in your androidManifest.xml):
public class MyApplication extends Application {
private ObjectGraph graph;
public ObjectGraph getGraph() {
return graph;
}
#Override
public void onCreate() {
super.onCreate();
graph = ObjectGraph.create(new Module(this));
graph.inject(this);
}
}
So the execution flow in a dagger app would be:
The android app starts and the MyApplication class builds the graph, parsing the #Module annotated classes and keeping an instance of it.
Then, the classes declared in the module can access its objects just injecting themselves in the object graph. Gradle then will evaluate their #Inject annotations and perform the dependency injections.
I guess Annotation Processing Tool requires that to generate code at the compile time.
This makes it Dagger can provide validation at compile time and not only at runtime.

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