What’s Wrong with Wrapping NavHostController in a Wrapper Class and Injecting it to Dependency Injection?

As a developer, you’re no stranger to finding creative solutions to complex problems. But sometimes, those solutions can lead to more harm than good. In this article, we’ll explore the pitfalls of wrapping NavHostController in a wrapper class and injecting it into dependency injection. Buckle up, folks, because we’re about to dive into the world of navigation and dependency injection!

The Problem: Over-Engineering a Solution

You’ve got a navigation-heavy app, and you want to make sure your NavHostController is properly managed. You’ve read about the benefits of dependency injection, and you think, “Why not wrap my NavHostController in a wrapper class and inject it into my app?” Sounds reasonable, right?

Wrong. Well, sort of. The problem isn’t that it won’t work; it’s that it’s an over-engineered solution to a problem that doesn’t exist. Let’s break it down:

• Unnecessary complexity: Wrapping NavHostController in a wrapper class adds an extra layer of complexity to your code. You’re creating a abstraction that doesn’t provide any real benefits.
• Tight coupling: By injecting the wrapper class into your app, you’re creating a tight coupling between your navigation and the rest of your app. This makes it harder to change or replace either component without affecting the other.
• Testability: With a wrapper class, you’re making it harder to test your navigation logic in isolation. You’ll need to test the entire wrapper class, which can lead to slower and more fragile tests.

The Solution: Keep it Simple, Stupid

So, what’s the alternative? Keep it simple, stupid! Instead of wrapping NavHostController in a wrapper class, use it as-is. Here’s why:

NavHostController is already a perfectly capable class that provides all the necessary functionality for navigation. By using it directly, you’re avoiding unnecessary complexity and keeping your code simple and easy to maintain.

// Fragment
private lateinit var navController: NavController

override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
    super.onViewCreated(view, savedInstanceState)
    navController = Navigation.findNavController(view)
}

In this example, we’re using Navigation.findNavController to get an instance of NavController. This is the recommended way to use NavController, and it eliminates the need for a wrapper class.

But What About Dependency Injection?

“Wait,” you might be thinking, “I thought dependency injection was all about decoupling components and making them easier to test?” You’re right! Dependency injection is a powerful tool, but it’s not always necessary.

In this case, NavController is a UI-related component that doesn’t need to be injected into your app. It’s a part of the Android Jetpack Navigation component, and it’s designed to be used as-is.

If you’re using a dependency injection framework like Dagger or Koin, you can still use it to inject other components that rely on NavController. Just don’t inject NavController itself.

// Using Dagger
@Module
class AppModule {
    @Provides
    fun provideSomeComponent(navController: NavController): SomeComponent {
        return SomeComponent(navController)
    }
}

In this example, we’re using Dagger to provide an instance of SomeComponent, which depends on NavController. This is a perfectly valid use of dependency injection.

But What About Testability?

“Okay, fine,” you might be thinking, “but how do I test my navigation logic without a wrapper class?” Great question!

The key to testing navigation logic is to use a combination of mock objects and Android’s built-in testing tools. Here’s an example:

// Test
@RunWith(AndroidJUnit4::class)
class NavigationTest {
    @get:Rule
    val navControllerRule = NavControllerRule(R.id.nav_host_fragment)

    @Test
    fun testNavigation() {
        // Set up your test scenario
        val navController = navControllerRule.getNavController()
        val scenario = launchFragmentInContainer()

        // Perform some navigation action
        navController.navigate(R.id.action_your_fragment_to_another_fragment)

        // Verify the result
        assertEquals(navController.currentDestination?.id, R.id.another_fragment)
    }
}

In this example, we’re using Android’s built-in testing tools to test our navigation logic. We’re using NavControllerRule to get an instance of NavController, and then we’re using Espresso to perform some navigation action and verify the result.

Conclusion

Wrapping NavHostController in a wrapper class and injecting it into dependency injection might seem like a good idea at first, but it’s an over-engineered solution to a problem that doesn’t exist. By using NavController as-is and keeping your code simple, you’re avoiding unnecessary complexity and making your code easier to maintain and test.

Remember, KISS (Keep it Simple, Stupid) is a powerful principle in software development. Don’t overthink it, and you’ll be just fine!

Wrapping NavHostController in a wrapper class and injecting it into DI	Using NavHostController as-is
Unnecessary complexity	Simple and easy to maintain
Tight coupling	Loose coupling
Harder to test	Easier to test

So, the next time you’re tempted to wrap NavHostController in a wrapper class and inject it into dependency injection, remember: simplicity is the best policy!

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