One of the lesser-discussed yet powerful features in the Kotlin ecosystem is Koin’s support for lazy modules and background loading. While experimental, these features can be crucial tools in your arsenal for building scalable and responsive applications. Stay tuned, this feature will be stable in the upcoming Koin 3.6 release 🔥
This blog post revisits these concepts, showing how you can leverage them to enhance your Kotlin applications.
Lazy loading is a design pattern commonly used to defer the initialization of an object until the point at which it is needed. It can significantly boost an application's performance by reducing initial load time. Koin, a lightweight dependency injection framework for Kotlin, integrates this concept beautifully through its support for lazy modules.
Lazy modules offer you the flexibility to delay resource initialization until they are actually required. To declare a lazy Koin module, utilize the lazyModule function. This strategy avoids upfront resource allocation, instead opting to load them in the background when Koin initiates. Here's a guide on how to define lazy modules 👇
In this example, m2 is a lazy module that provides ClassB. m1 is another lazy module that includes m2 and provides ClassA, binding it to IClassA. The includes method allows you to nest lazy modules, organizing your dependency graph elegantly and efficiently.
Lazy modules will not trigger any resource allocation until they have been explicitly loaded. This lazy loading mechanism ensures that your application remains light and responsive, loading only what it needs, when it needs it.
Once you've defined your lazy modules, Koin allows you to load them in the background, leveraging Kotlin coroutines. This asynchronous loading can significantly improve your application's startup time and overall performance. Your application’s startup time is minimized, and resources are used as efficiently as possible.
A key enhancement to consider is the hybrid loading strategy, where 20% of the application's core components are loaded synchronously to quickly display the first screen, while the remaining 80% are loaded asynchronously. This approach ensures that users are immediately greeted with a responsive UI, while the bulk of the application's resources are efficiently loaded in the background, optimizing both startup time and performance.
To implement this, define the critical components needed for the initial screen in a standard Koin module, and load this synchronously within your startKoin block. The rest of your components, not immediately required, should be defined in lazy modules, and set to be loaded asynchronously.
This balanced approach allows for an immediate user interaction layer while efficiently managing resource loading and application initialization in the background.
Beyond just defining lazy modules, Koin enables these modules to be loaded in the background, thanks to the power of Kotlin coroutines. This asynchronous loading further optimizes the application’s performance and responsiveness. To load your lazy modules in the background, you can use the KoinApplication.lazyModules function within your startKoin block. Koin provides several utility functions to manage this process, including waiting for all start jobs to complete or running code after the loading is finished:
By default, Koin uses Kotlin's Dispatchers.Default for coroutine execution. However, the lazyModules function allows you to specify a different dispatcher, such as Dispatchers.IO, tailoring the background loading process to your application's specific needs.
Although these ideas of lazy modules and background loading are well-established, they're often underestimated, yet they have tremendous potential in enhancing Kotlin applications. By integrating these features, you can unleash a higher level of responsiveness, efficiency, and scalability within your applications.
Let's go🔥