How can you decouple your mobile app code with dependency injection?

If you are a mobile app developer, you probably know the importance of writing clean, modular, and testable code. But how can you achieve that without creating tight couplings and hard dependencies between your classes and components? One way is to use dependency injection, a design pattern that helps you decouple your code and make it more flexible and reusable. In this article, you will learn what dependency injection is, how it works, and how you can apply it to your mobile app code using some common frameworks and tools.

1 What is dependency injection?

Dependency injection (DI) is a technique that allows you to pass the dependencies of a class or a component as parameters to its constructor or setter methods, instead of creating them inside the class or component. This way, you can avoid hard-coding the dependencies and make them interchangeable and configurable at runtime. For example, if you have a class that needs a database service to perform some operations, you can inject the database service as a dependency to the class, instead of creating a new instance of the database service inside the class. This way, you can easily switch the database service with another one, or mock it for testing purposes.

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Santosh Botre

Lead Technical Architect
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Dependency injection allows us to separate the creation and management of dependencies from the core logic of a class or struct. The members of the class or struct will be instantiated and passed to the class/struct object from outside the class. Using interface or protocol driven implementation helps to avoid tight coupling and easy to test the code by creating Mocks and providing mock implementation for the methods like network calls etc.

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2 Why use dependency injection?

Dependency injection offers several benefits for your mobile app code, such as reducing the coupling between classes and components, making them more independent and modular. This improves the readability, maintainability, and reusability of your code. Furthermore, dependency injection increases the testability of your code, as you can easily isolate and mock the dependencies of your classes and components. Additionally, it enables the inversion of control (IoC) principle, which states that control flow should be determined by external factors rather than by your code. This allows you to delegate the responsibility of creating and managing the dependencies to an external entity like a DI container or framework, which can handle the dependency resolution and injection for you.

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Santosh Botre

Lead Technical Architect
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It help us to achieve majorly few things - decoupling - testability - reusability - code readability - modularity - maintainability - scalability

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3 How to use dependency injection?

When implementing dependency injection in mobile app code, there are various approaches depending on the language and platform used. Constructor injection is the most common and preferred type, as it guarantees that all necessary dependencies are present before instantiation and makes them explicit and immutable. Setter injection is useful for optional or dynamic dependencies that may change over time, or when injecting dependencies after instantiation. The least common and recommended type of dependency injection is property injection, since it exposes the dependencies to the outside world and makes the class or component vulnerable to null or invalid dependencies.

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4 What are some dependency injection frameworks and tools?

When developing a mobile app, various dependency injection frameworks and tools can be utilized to help you implement dependency injection in your code. Dagger is a popular DI framework for Java and Android that uses annotation processing and code generation to create and inject the dependencies. Koin is a lightweight DI framework for Kotlin and Android using a DSL and functions to define and inject the dependencies. Hilt is an extension of Dagger that simplifies DI setup and configuration for Android apps, providing predefined components and scopes. Swinject is a powerful DI framework for Swift and iOS that uses a DI container and registration/resolution methods. Resolver is a lightweight DI framework for Swift and iOS that uses property wrappers and global registries. All of these frameworks support constructor injection, setter injection, and property injection.

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5 How to apply dependency injection to your mobile app code?

To apply dependency injection to your mobile app code, you need to identify the dependencies of your classes and components, and make them abstract or interface-based. After that, you should choose the type of dependency injection that suits your needs and preferences, and inject the dependencies as parameters to their constructors, setters, or properties. Utilizing a dependency injection framework or tool that supports your language and platform is also recommended in order to delegate the dependency resolution and injection to an external entity. Lastly, testing your code with different implementations or mocks of your dependencies is important for ensuring the quality and reliability of your code.

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