Koin and Ktor: The Kotlin Dynamic Duo

In the realm of Kotlin-based web development, Ktor has emerged as a powerhouse framework for crafting web applications and APIs. Its simplicity and adaptability have captivated a growing community of developers. Within this vibrant ecosystem, Koin, our popular dependency injection (DI) framework, takes centre stage in bolstering Ktor's capabilities.

In this blog post, we'll dive into the ways Koin empowers Ktor applications with efficient Dependency Injection, while also exploring the latest updates in the world of Koin.

Ktor and Koin: A Powerful Kotlin Duo

To truly grasp the power of the latest Koin update, let's first explore the seamless synergy between Ktor and Koin. Ktor, a lightweight yet feature-rich framework, empowers developers to create asynchronous and scalable web applications in Kotlin. In parallel, Koin, a robust DI framework, simplifies the management of dependencies in Kotlin applications. Together, these two technologies form an unstoppable force in the world of Kotlin-based web development.

The seamless integration of Koin with Ktor empowers you to effortlessly inject dependencies into your Ktor applications, unlocking the potential for enhanced modularity, streamlined code organization, and simplified testing. This integration goes beyond mere compatibility, as it harnesses the power of Koin to amplify the capabilities of Ktor.

Koin Update

Koin has just unveiled its latest versions, 3.5.0 & and 3.5.1, packed with a multitude of new features, improvements, and enhancements. This update, which was released in September of 2023, demonstrates the unwavering commitment of the Koin development team together with Koin's dedicated community of contributors to deliver a dependable and cutting-edge DI solution for Kotlin applications.

Let's take a look at what's included in Koin 3.5.1:

📙 Koin updated to Ktor's Latest Version 2.3.3: This means that you can now harness the full potential of Koin within the latest version of Ktor, taking advantage of its features and enhancements to create even more robust web applications.

⚒️ Better Context Isolation: Koin's integration allows Ktor to create separate contexts for different parts of your application, ensuring that dependencies are injected correctly without interference from other parts of your codebase. This enhancement improves code organization and makes debugging and maintenance more straightforward.

🔮 Request scope to allow injection for request duration: Request scope enables the injection of dependencies that are specifically tied to the duration of a single HTTP request. This is particularly useful when you need to manage resources or states that should be created and disposed of per request. Koin seamlessly integrates with Ktor to provide this functionality, making it easier than ever to manage request-specific dependencies.

Harnessing Koin in Your Ktor Application

Now that we've covered the latest Koin-Ktor update, let's explore how you can harness Koin's power in your Ktor application for efficient dependency injection👍

Install Koin Plugin

To begin using Koin in your Ktor project, install the Koin plugin like 👇

💡The Koin plugin for Ktor functions within its own isolated Koin context. This means that Koin must be configured and started within Ktor itself. Starting Koin outside of Ktor is not a supported approach.

Injecting Dependencies in Ktor

Once you've installed the Koin plugin, injecting dependencies becomes a breeze with the inject() and get() functions provided by Koin. These handy functions can be used within the Application, Route, and Routing classes. Let me show you an example of how to inject a HelloService 👇:

Resolving Dependencies within Ktor Request Scope

With Koin 3.5.0 and later, you can declare components that live within the Ktor request scope timeline. To achieve this, declare your component within a scope<RequestScope> section, like👇

Then, within your HTTP call, you can easily resolve the dependency using call.scope.get<ScopeComponent>()👇

This ensures that scope instances are created and dropped for each request, providing a clean and efficient way to manage dependencies 😍

Running Koin from an External Ktor Module

If you're working with Ktor modules, you can load specific Koin modules by declaring them using the koin { } function 👇