Sharing Code Between Platforms in Kotlin Language

Introduction to Sharing Code Between Platforms in Kotlin Language

Kotlin’s versatility extends beyond its impressive syntax and functionality it offers the ability to share code across multiple platforms, making it a standout choice for cross

-platform development. Sharing code between platforms in Kotlin is achieved through Kotlin Multiplatform, a powerful feature that allows developers to write reusable code for different operating systems like Android, iOS, Web, Desktop, and even servers. This approach is particularly beneficial in projects that require building applications for diverse environments, all while maintaining a unified codebase. In this article, we’ll explore how Kotlin allows sharing code between platforms, discuss key concepts such as expect/actual declarations, and examine practical use cases.

What Is Kotlin Multiplatform?

Kotlin Multiplatform, or KMP, is a tool that enables developers to share code between different platforms and retain the ability to write platform-specific code where necessary. KMP separates common logic from platform-dependent logic, therefore allowing flexibility in reusing core functionality across multiple platforms while writing custom implementations for each and every platform’s unique requirements.

For example, when developing an application for both Android and iOS, with Kotlin Multiplatform you could write all the business logic, networking, and data manipulation code once in a shared module. The platform-specific code, like UI handling or specific APIs, would then be handled separately.

Structure of a Kotlin Multiplatform Project

A Kotlin Multiplatform project has common code, but the platform-specific code is isolated to specific platform modules. You can write reusable logic in a common module and the necessary logic depending on the platform in dedicated platform modules – Android, iOS, or JVM.

1. Common Module

The common module is where all shared code exists. It holds the independent logic for the platform, which could be business rules, data models, and utility functions; indeed, it defines the basic functionality which needs to hold good for all the other platforms.

// Common module code example
class Greeting {
    fun sayHello(): String = "Hello from shared code!"
}

Such an example is that of using a class Greeting without any changes on Android, iOS, or any other device. The class contains just general, platform-independent logic.

2. Modules Specific to Platforms

Kotlin Multiplatform also allows you to write platform-specific code as modules, unrelated to each other. These modules are to address features dependent on the platform: user interface rendering or a native API. This is where Kotlin’s flexibility really shines: even if you share core code, you still can write custom implementations for those unique requirements of each platform.

Kotlin therefore manages the various implementations where the use of expect and actual keywords applies. The expect keyword declares a function or class in the common module, while the actual keyword provides platform-specific implementation.

// Common module
expect fun getPlatformName(): String

// Android module
actual fun getPlatformName(): String {
    return "Android"
}

// iOS module
actual fun getPlatformName(): String {
    return "iOS"
}

Let’s declare the getPlatformName() function in the common module, but its implementation is different for Android and iOS, so it will allow us to have platform-specific behavior.

3. Gradle Configuration

For Kotlin Multiplatform projects, Gradle is used for build configuration. The build.gradle.kts file contains information about specifying the target platform for each one. Here’s how to do that within a Gradle file:

kotlin {
    android()
    ios()

    sourceSets {
        val commonMain by getting
        val androidMain by getting
        val iosMain by getting
    }
}

This configuration specifies the commonMain source set for shared code and separate source sets for Android (androidMain) and iOS (iosMain). With this setup, you can begin writing platform-specific code while sharing core logic.

Practical Use Cases for Sharing Code in Kotlin

1. Business Logic Sharing

One of the most common use cases is sharing business logic between platforms. Any logic that governs how your application behaves, such as validation, calculations, or decision-making processes, can be written once in the common module and reused across platforms.

For example, you might implement the logic for calculating a user’s score in a game or managing business rules in an e-commerce app in the shared code, and then use this logic on both Android and iOS without duplication.

2. Networking

Networking code, such as API requests or data synchronization, is often platform-agnostic and can be shared between platforms. Using libraries like Ktor, you can write shared networking code that handles HTTP requests in the common module, while platform-specific concerns (such as configuring permissions on Android) are handled separately.

// Shared networking code using Ktor
import io.ktor.client.*
import io.ktor.client.request.*

suspend fun fetchDataFromApi(url: String): String {
    val client = HttpClient()
    return client.get(url)
}

This code can be shared across platforms to make API requests from both Android and iOS apps.

3. Data Persistence

Kotlin Multiplatform also allows sharing code for data persistence. For example, if you use a database for storing user data, you can implement the database access logic in the common module using libraries like SQLDelight, and this logic can be shared across platforms.

4. Utilities and Helper Functions

Utility functions, such as string manipulation, date formatting, or common algorithms, are perfect candidates for shared code. These utility functions tend to be platform-independent and can be reused easily across multiple environments.

Tools and Libraries for Kotlin Multiplatform

Several libraries and tools help streamline Kotlin Multiplatform development and make sharing code easier. Some notable tools include:

1. Ktor: For networking across platforms.
2. SQLDelight: For cross-platform database access.
3. Kotlinx Serialization: For serializing and deserializing data in shared code.
4. Kotlinx Coroutines: For managing asynchronous tasks across platforms.
5. Multiplatform Settings: For handling shared preferences or key-value storage.

These libraries are designed with Kotlin Multiplatform in mind, making it easier to write shared code that can be reused across different platforms.

Kotlin Multiplatform vs. Other Cross-Platform Solutions

Kotlin Multiplatform takes a different approach to cross-platform development than frameworks like React Native or Flutter, which focus on writing a single UI codebase for all platforms. In contrast, it emphasizes sharing core business logic while keeping the UI and platform-specific code separate.

Differences:

• UI Flexibility: Kotlin Multiplatform allows for native UI development on each platform, unlike frameworks that try to unify the UI.
• Target Platforms: Kotlin Multiplatform supports a wider range of platforms, including Android, iOS, Web, JVM, and more.
• Gradual Adoption: KMP can be integrated gradually into existing projects, making it easier to adopt without a complete rewrite.

Advantages of Sharing Code Between Platforms in Kotlin Language

By using the Kotlin Multiplatform, developers share code for multiple platforms like Android, iOS, and web applications with improved development efficiency and code quality. The benefits of sharing code between platforms in Kotlin make this approach valuable for modern cross-platform developments.

1. Increased Code Reusability

Sharing of codes among the different platforms enables programmers to reuse common logic across various applications, thus eliminating redundancy.

• Single Source of Truth: Business rules, data models, algorithms, etc., could be coded once and then used across all platforms (Android, iOS, etc.) avoiding inconsistencies and errors caused by duplicated code.
• Eliminates Duplication: Developers will not have to separately maintain code bases for common functionality across different platforms thus eliminating duplication of efforts and maximizes productivity.

2. Faster Development

The benefit of writing code that can run on several platforms is that it accelerates dramatically the delivery of applications from development teams.

• Faster Time to Market: Since most of the code is shared, developers need to work only on platform-specific features like UI while reusing shared logic, so they get faster development cycles and releases.
• Simplified Maintenance: When a bug in shared code is fixed or feature added, then updates can occur automatically across all platforms without the need for platform-specific fixes and quickening the cycle of maintenance.

3. Consistency Across Platforms

Code sharing will maintain core logic across the platforms to reduce chances for inconsistency.

• Uniform Business Logic: The same mechanisms of error handling, as well as the same data processing and validation mechanisms, will be ensured on every platform, making the user experience much more reliable.
• Synchronized feature releases: It will be possible to have code sharing for the administration of feature updates between different platforms in a synchronized manner thus ensuring there is a parities in feature implementation as well as behavior that is consistent between Android and iOS as well as web applications.

4. Easy Code Management

The use of shared logic makes it easier for teams to manage their code since all the logic is encapsulated in a single code base.

• Shared codebase: With a shared codebase comes the ability to work in one place for updates, improvements, or refactoring, which makes code management easier and has fewer chances of bugs specific to platforms because of inconsistent implementations.
• Simplified Testing: Shared code can be tested once and then applied across platforms, removing efforts in duplicated testing across the different platforms. Automated testing of shared modules will also ensure that fundamental logic behaves exactly the same way on all the platforms.

5. Lower Development Costs

Using shared code will, in fact decrease the development costs in projects meant for more than one platform as the shared modules’ testing and debugging efforts may be done only once.

• Fewer Heads: The teams could become more focused with less number of developers maintained in different codebases for different kinds of platforms. One team could accomplish the shared logic as well as the platform-dependent pieces.
• Scaling with relatively minimal added cost: when adding new platforms such as web or desktop applications, it costs much less than scaling applications since most aspects of the application’s core already exist in the shared codebase.

6. Better Code Quality

A more general, well-tested codebase toward a better overall code quality would be promoted by code sharing among platforms.

• Fewer Platform-Specific Bugs: A centralized codebase minimizes the chances of inherent platform-specific bugs. Platform-specific bugs brought along with centralization in one codebase would result in a more stable and reliable application on all platforms.
• Better Maintainability: Shared code is more modular and easier to maintain since the developers would be prompted to write reusable, clean, well-documented code which serves more than one platform.

7. Implicitly Seamless Interoperability with Native Features

Kotlin Multiplatform lets you share common logic while still keeping an ability to write the necessary platform-specific code.

• Platform-specific extensibility-Code where possible: UI, hardware access, etc. may be coded. Shared logic might be made use of both at the same time. It provides flexibility to vary features on platforms without compromising the advantage of shared code.
• Native APIs can be directly integrated: Kotlin interoperability with Java and Swift is very good and developers can easily make use of shared Kotlin code along with platform-specific APIs on Android as well as iOS.

8. Enhance Collaboration Among Platform Teams

It encourages better collaboration among teams involved in building platform-specific interfaces, thereby leading to a more cohesive development process.

• Cross-Platform Collaboration: It makes it possible for the Android and iOS developers to work on the same shared code base, thus enhancing the sharing of knowledge and silos reduction among platform-specific teams.
• Unified Code Reviews: Since most of the code is shared, platform teams can participate in the code reviews and give comments on the shared logic that leads to better quality code and collaboration.

Disadvantages of Sharing Code Between Platforms in Kotlin Language

While Kotlin Multiplatform does present a multitude of advantages when sharing code between platforms, it also comes with disadvantages for which developers should be alerted. Such disadvantage conditions can result in the complexity of development, performance, and project management. Below are the most crucial disadvantages of code sharing across platforms on Kotlin.

1. Limited Platform-Specific Features

Kotlin Multiplatform supports common code sharing, though platform-specific features are not fully supported thus presenting specific limitations.

• UI and Hardware Access: Platform- specific UI elements or hardware features (camera, GPS, etc) cannot be implemented correctly in the shared codebase; hence developers will need to write different code for every platform, which is cumbersome.
• Complex API Compatibility: Not all APIs (e.g., Android, iOS) available on different platforms can be easily accessible in the shared code; hence sharing of code is not so efficient and may raise platform-specific integration complexity.

2. Increased Complexity in Project Structure

Sharing code for multiple platforms sometimes causes a more complex project structure and increases the amount of work involved with management of the codebase.

• Multiplatform Configuration: The setup for a project that shares code between platforms entails rather tricky build configurations, especially when one or more targets would be Android, iOS, web, etc. This makes the project setup hard and time-consuming.
• Multiple Build Systems: Developers must be familiar with Gradle for Android and Xcode for iOS or other build tools depending upon the platforms, adding a complexity layer to the development workflow.

3. Performance Overhead

Code sharing may also add another layer of performance overhead due to compatibility layers or usage of some library in a platform-dependent way.

• Cross-Platform Abstractions: Shared code may eliminate some platform-specific optimizations to be replaced with more generic substitutes. This would mean that the final performance on these specific platforms may not be at the optimum level.
• Differences in Execution: The same shared logic, though written at compile-time, might behave differently on different platforms because of the respective OS or runtime under which those platforms exist, thus requiring additional optimizations or tweaks particular to those platforms.

4. Dependency Management Issues

Third-party libraries in a Kotlin Multiplatform project can create several dependencies. This makes the management of them rather challenging.

• Library Compatibility: Not all libraries used in Kotlin support Kotlin Multiplatform. Developers will have to find alternative libraries or maintain platform-specific wrappers, further delaying the time to develop.
• Dependency Conflicts: Dependency conflicts occur due to handling versions of dependencies specifically for a platform. The build process may also get complicated, which delays development.

5. Debugging and Testing Challenges

Debugging and testing shared code that uses multiple platforms can be burdensome, especially if platform-specific bugs are observed.

• Platform-Specific Bugs: Although shared code has reduced the amount of duplicated code, it also implies that one bug in the shared code can affect more than one platform. Debugging these issues could be challenging, especially if their manifestation is different across the various platforms.
• Limited Cross-Platform Testing: The testing tools of Kotlin Multiplatform are not very mature or fully integrated across all the platforms. Hence, it is difficult to ensure shared code behavior in different environments.

6. Steeper Learning Curve

The learning curve for Kotlin Multiplatform is steeper, especially for those developers who are not accustomed to Kotlin or cross-platform development.

• Specialized Knowledge: Developers need to be familiar not only with Kotlin but also with the development environment for the specific platforms (Android, iOS, web). During their work, they have to keep cross-platform code alive and solve platform-specific parts, which can be difficult for teams inexperienced in this respect.
• Complex Tooling: Creating and maintaining a Kotlin Multiplatform project involves intricate knowledge of multiple build systems, integrations with various IDEs, and so many tools. This introduces complexity and slows down development initially.

7. Limited Community and Ecosystem Support

Kotlin Multiplatform is slowly growing but the ecosystem support and community is not as rich as native development environments.

• Fewer Resources and Tutorials: Less documentation, resources, and tutorials are there compared to the native Android or iOS development; hence developers can’t get help easily or solve problems.
• Third-party libraries support: The Kotlin multiplatform ecosystem is still relatively young; therefore, third-party libraries may not be compatible with the multiplatform model. This may inhibit the availability of as many tools and libraries as one may get in cross-platform development.

8. Incomplete Platform Integration

As much common logic Kotlin Multiplatform shares, some of the entities in development still need to be addressed and dealt with platform after platform.

• Development Fragmentation: Even when full code sharing is attempted, developers still need to handle the UI layers and other parts of the development as discreet for different platforms, making the development partially fragmented. It also threatens the pursuit of full code sharing and gives rise to what could be a more complex code.
• Native-Specific Tools: Although native-specific tools such as Android Studio or Xcode are necessary for particular tasks, their use can also lead to context switching as well as fractures the development experience for teams working on both platforms.