Using UseCases in Android Development

As an Android developer, you may have heard about UseCases. They are a powerful architectural pattern that helps you write modular, testable, and maintainable code. In this post, we will explore what UseCases are, how they work, and how to use them in your Android app.

What are UseCases?

A UseCase is an abstraction of a task that your app needs to perform. It represents a specific business logic that you want to execute in your app. UseCases are responsible for orchestrating the interactions between the different layers of your app, such as the UI, the data layer, and the network layer.

Using UseCases, you can decouple your app's business logic from the rest of your code, making it easier to write, test, and maintain. By separating your app's functionality into smaller UseCases, you can easily swap out or modify individual UseCases without affecting the rest of your codebase.

How do UseCases work?

UseCases are typically created as classes or objects that expose a single method for executing the specific task that they represent. For example, you might create a UseCase to fetch a list of data from a remote API, or a UseCase to save data to a local database.

Inside the UseCase, you can define the specific steps that are required to complete the task. This might involve calling multiple methods from different layers of your app, such as the data layer or network layer.

Once the UseCase has completed its task, it typically returns a result to the caller, such as a list of data, a success or error message, or a boolean value indicating whether the task was successful or not.

How to use UseCases in your Android app

To use UseCases in your Android app, you first need to identify the specific tasks that your app needs to perform. This might involve analyzing your app's requirements and defining the specific business logic that you want to implement.

Once you have identified your app's UseCases, you can start implementing them as classes or objects in your app's codebase. For example, you might create a UseCase to fetch a list of data from a remote API, or a UseCase to save data to a local database.

Inside the UseCase, you can define the specific steps that are required to complete the task. This might involve calling multiple methods from different layers of your app, such as the data layer or network layer.

To use the UseCase in your app's UI, you can simply create an instance of the UseCase and call its execute method. For example:

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1val fetchUserDataUseCase = FetchUserDataUseCase(userRepository)
2fetchUserDataUseCase.execute(userId) { result ->
3    // Handle the result here
4}

In this example, we are creating an instance of the FetchUserDataUseCase and passing in a userRepository as a dependency. We are then calling the execute method of the UseCase, passing in a userId as a parameter.

When the UseCase has completed its task, it will call the callback function that we passed in as a parameter, passing in the result of the task as an argument. We can then handle the result in our UI code as needed.

Benefits of using UseCases

There are several benefits to using UseCases in your Android app:

• Modularity: UseCases allow you to modularize your app's business logic, making it easier to understand and maintain.
• Testability: UseCases are easy to test in isolation, as they typically have clear inputs and outputs. This makes it easier to write automated tests for your app's functionality.
• Reusability: UseCases can be reused across your app's codebase, making it easy to swap out or modify individual UseCases without affecting the rest of your code.
• Separation of concerns: UseCases allow you to separate your app's business logic from the rest of your code, making it easier to reason about and modify.

Example UseCase

Let's look at an example UseCase to see how it works in practice. In this example, we will create a UseCase to fetch a list of data from a remote API.

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1class FetchDataUseCase(private val apiService: ApiService) {
2
3    fun execute(callback: (Result<List<Data>>) -> Unit) {
4        apiService.getData().enqueue(object : Callback<List<Data>> {
5            override fun onResponse(call: Call<List<Data>>, response: Response<List<Data>>) {
6                if (response.isSuccessful) {
7                    callback(Result.Success(response.body()!!))
8                } else {
9                    callback(Result.Error(Exception("Failed to fetch data")))
10                }
11            }
12
13            override fun onFailure(call: Call<List<Data>>, t: Throwable) {
14                callback(Result.Error(t))
15            }
16        })
17    }
18}

In this example, we are creating a UseCase called FetchDataUseCase. It takes an instance of ApiService as a dependency, which is responsible for fetching the data from the remote API.

The UseCase exposes a single method called execute, which takes a callback function as a parameter. This callback function will be called when the UseCase has completed its task.

Inside the execute method, we are calling the getData method on the apiService instance, which returns a Call object that represents the network request.

We are then attaching a callback function to the enqueue method of the Call object, which will be called when the network request is complete.

If the network request is successful, we are calling the callback function with a Result.Success object, passing in the list of data that was returned by the API.

If the network request fails, we are calling the callback function with a Result.Error object, passing in an Exception that indicates the error that occurred.

Conclusion

In conclusion, UseCases are a powerful architectural pattern that can help you write modular, testable, and maintainable code in your Android app. By separating your app's business logic into smaller UseCases, you can easily swap out or modify individual UseCases without affecting the rest of your codebase.