Hello Dev, Here is the list of the most frequently asked questions of Dagger in interviews with answers. 

As we know Dagger is a part of Android MVVM architecture click here to know more about Dagger in Android. Let’s dive into the view model questions directly.

1:- What is Dagger in Android, and why is it used?

Dagger is a dependency injection framework for Android and Java. It’s used to manage the dependencies in an application and provides a way to create and inject objects efficiently.

2:- Explain the difference between compile-time and runtime dependency injection. How does Dagger relate to compile-time injection?

Compile-time dependency injection is done at compile time, where dependencies are resolved and generated by the Dagger annotation processor before runtime. Dagger is a compile-time dependency injection framework, which means it generates code during compilation to handle dependency injection.

4:- What is the main advantage of using Dagger over manual dependency injection?

Dagger eliminates the need for writing boilerplate code for dependency injection, making the codebase cleaner and more maintainable. It also provides compile-time checks, which can catch dependency-related issues early in the development process.

5:- Explain the terms “Dependency,” “Dependency Injection,” and “Inversion of Control (IoC)” in the context of Dagger.

A dependency is an object or service that another class relies on. Dependency Injection is the process of providing these dependencies to a class from the outside, typically through constructor injection or method injection. Inversion of Control is a design principle where control over the flow of a program’s execution is inverted from the program to a container or framework, like Dagger, which manages object creation and dependency injection.

6:- What are the key components of Dagger, and what roles do they play?

  • Dagger consists of three key components: Modules, Components, and Injectors.
  • Modules provide information on how to construct dependencies.
  • Components are interfaces that define the dependency graph and how to access dependencies.
  • Injectors are classes generated by Dagger that inject dependencies into client classes.

7:- Explain the purpose of Dagger Modules and how they are used in dependency injection.

Dagger Modules are used to provide instructions to Dagger on how to create and provide instances of dependencies. They define methods annotated with @Provides that return instances of classes, which Dagger uses to fulfill dependencies.

8:- What is the purpose of the @Component annotation in Dagger, and how is it used?

The @Component annotation is used to define a Dagger component interface. Components specify the dependencies that can be injected and create a bridge between the modules and the injection points in your code.

9:- How does Dagger ensure that the right dependencies are injected into classes that request them?

Dagger uses compile-time code generation to analyze the dependency graph defined in the component interfaces. It generates code that ensures the correct dependencies are provided and injected where needed.

10:- Explain the difference between @Singleton scope and custom scopes in Dagger.

@Singleton is a built-in scope in Dagger that indicates a single instance of a dependency should be shared across the entire application. Custom scopes allow you to define your own scopes with specific lifetimes for dependencies, such as per-activity or per-fragment scopes.

11:- How do you handle constructor injection in Dagger, and why is it considered a best practice?

Constructor injection involves providing dependencies through a class’s constructor. It is considered a best practice because it makes dependencies explicit, promotes testability, and allows for easier substitution of implementations during testing.

12:- What are Dagger Subcomponents, and when would you use them?

Dagger Subcomponents are components that are nested within other components. They allow for a more granular organization of the dependency graph and can be used when you have submodules or subscopes within your application.

13:- What is Dagger Android, and how does it simplify dependency injection in Android applications?

Dagger Android is a set of Dagger extensions specifically designed for Android. It provides annotations and classes to simplify common Android dependency injection patterns, such as injecting into activities, fragments, and services.

14:- How can you handle Dagger component creation and setup in a multi-module Android project?

 In a multi-module project, Dagger components can be set up at different module levels, and dependencies can be exposed through the component interfaces. Subcomponents or component dependencies can also be used to connect modules.

15:-Can you use Dagger with Kotlin in Android projects, and are there any Kotlin-specific considerations to keep in mind?

Yes, Dagger works seamlessly with Kotlin in Android projects. You can use Kotlin’s data classes and default arguments to simplify Dagger setup and reduce boilerplate code.

16:- How can you write unit tests for classes that use Dagger for dependency injection?

 You can write unit tests for Dagger-injected classes by providing mock or test-specific modules during testing. You can also create Dagger components for testing that override module bindings to provide test doubles.

18:- Explain the concept of Dagger Hilt and how it relates to Dagger in Android development.

Dagger Hilt is a dependency injection library built on top of Dagger, designed specifically for Android. It simplifies Dagger setup and provides predefined annotations and components tailored for Android development.

19:-Why do we use the Dependency Injection Framework like Dagger in Android?

  • It Optimizes performance and memory usage as it avoids the creation of instances 
  •  It helps us manage the complex dependencies easily. 
  • It makes unit testing easy by enabling us to pass all the dependencies from outside so that
    we can easily use the mocked objects. 
  • It easily manages the scope(lifecycle) of the object. 

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