Kotlin

To me, using functions as properties in the primary constructor of a data class is a code smell. Here’s why: Data classes represent data. Data is a value. Data is never executed. Functions are not data. They produce values when executed. Note: By the book, a function returns a value, while a procedure executes commands. In both cases, neither is data. Why It Matters Kotlin generates key methods for data classes based on the properties in the primary constructor, such as:...

Sharing tests across Kotlin Multiplatform (KMP) projects can be tricky when dealing with platform-specific APIs like Android’s Bundle. commonTest on Android relies on the androidTest source set, which uses an empty android.jar, leading to test failures. The Solution The ideal solution is to avoid platform-specific APIs in commonTest. If that’s not an option, you can use Robolectric in your commonTest source set to access functional Android classes. This approach: Allows testing of platform-specific code in commonTest....

Heads-up: this article assumes familiarity with Kotlin’s extension functions and expect and actual declarations in Kotlin Multiplatform (KMP). My work has recently focused on “commonizing”1 APIs, and I came across KT-70012, which I believe merits attention. In Kotlin JVM development, the EXTENSION_SHADOWED_BY_MEMBER warning indicates that an extension function is redundant, as it will always be overshadowed by a member function with the same name when invoked. However, in KMP, this behaviour can be useful, as shadowing may occur on some platforms but not all....

Disclaimer: It has been brought to my attention the title can be seen as a click bait. That wasn’t my intention and I’m sorry. I wanted to reference the Fallout game series and the No Mutants Allowed community. Testable code plays a crucial role in app development. When we neglect designing code for testability, we often resort to using a mock library (such as Mockito Kotlin, also know as “auto-mockers”) as a mean to achieve test coverage....

Android has made significant progress in becoming a DI-Friendly Framework. Throughout the years, new APIs like AppComponentFactory and FragmentFactory have been introduced, allowing apps to incorporate their own custom constructors and facilitating the development of testable code. The purpose of this article is to highlight some of the Android APIs that are utilised behind the scenes. By exploring these APIs, developers can gain a better understanding of the underlying mechanisms employed by popular libraries (such as Dagger Hilt and Koin Android)....

A few weeks ago, I had to create an extension function - a usual task for any Kotlin developer. But there were a few limitations: The receiver was a common type, polluted with too many methods. The extension function was only relevant to my feature package. Creating a Gradle module was out of scope. Introducing a new type to hold the function felt like too much. Kotlin doesn’t support package-private, yet....

Modeling is a critical task in Software Development: good models reduce the risk of bugs, increase readability and improve maintainability. However, we can often see developers focusing on “How can I code this?”, and they are done with their task when they find a way to code it. This inherently reduces the domain modeling to the abuse of primitives and shallow design where any inconsistent state is allowed. To better explain, let’s consider the hypothetical requirements:...

The Android Community has long advocated that Activities and Fragments were views - but this perception has changed over time. For good. Let’s dive deep into how to design views and view models, how they wire to a LifecycleOwner, and how this can positively impact your’s app testability. To better describe how to build humble views we will be developing an elementary Sign-Up form with an email, a password text field and two buttons: a cancel that pops the user’s back stack and a sign up that creates an account and moves the user to the home screen....

When discussing Factory Methods, extension functions are often preferred in Kotlin. However, naming these functions in a discoverable way without cluttering your project’s namespace can be challenging. A great source of inspiration is Kotlin’s Standard Library, which offers numerous examples to guide function design. Wrapping an Instance If you want to take an existing instance and adapt it to a different object to meet another contract—such as creating a ViewModelProvider.Factory that internally uses a javax....