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One such powerful solution for cross-platform mobile application development with shared business logic is Kotlin Multiplatform Mobile. Developed by JetBrains, KMM enables sharing of code between iOS and Android, hence reducing the time and effort of development considerably. By leveraging Kotlin, a modern expressive programming language, KMM empowers developers to write clean and efficient code while maintaining native performance and flexibility.
One of the things that really sets KMM apart from most of the other cross-platform solutions out there is that it doesn't attempt to completely abstract away platform-specific features. On the contrary, the technology provides a common codebase for the core logic while still allowing free access to native APIs for the purposes of implementing both platforms' specific functionalities. The resulting hybrid architecture therefore combines the best of both worlds: shared business logic and a native user experience, allowing the developer to have full control over how the applications are structured.
KMM will work the most for teams that want to simplify the development process by eliminating redundant work while maintaining the high bar of native quality for the end users. Its adoption is happening organically because of its ease of integration with existing projects and tools, and hence, it's going to be one of the versatile choices for mobile development in 2024 and beyond.
KMM is built on top of Kotlin, an official first-class language for Android development announced by Google in 2017.
The evolution of KMM first showed up when Kotlin 1.2 had been released in 2017, which had the first look of Kotlin's multiplatform capability. This version allowed developers to write shared code that could be compiled to multiple platforms, but at the time the focus was more on Kotlin/JVM and Kotlin/JS. It wasn't until the release of Kotlin 1.3 that Kotlin/Native-which enables Kotlin to be compiled to native binaries for iOS among other platforms-really gained more prominence in late 2018.
Kotlin/Native marked a significant turn of events in the journey of Kotlin to multiplatform status. Initially, Kotlin/Native targeted non-Android platforms such as iOS, Linux, and Windows. This really opened the gates for cross-platform development with Kotlin, which made shared business logic and reusable libraries across various platforms possible. However, the development experience was fragmented in the early stages and the ecosystem was still immature-with limited support for mobile-specific features.
Besides, JetBrains started to refine the multiplatform capabilities of Kotlin, noticing the chance for this language to be cross-ecosystem. In 2019, it officially announced Kotlin Multiplatform Mobile, or KMM in short. KMM was meant to operate within the frames of mobile development exclusively, allowing developers to write shared code in Kotlin both for Android and iOS applications. This was a reaction of necessity, since the demand for cross-platform solutions that did not make any compromises in native performance or user experience was growing louder.
KMM was able to find a sweet spot by being pragmatic regarding code sharing. Not a "write once, run anywhere" sort of philosophy, but KMM advocates for the sharing of only the logic and the core modules of the app and everything else, like UI or other platform-specific components, remaining native. This hybrid model offers all the advantages of code reuse yet is still able to provide specific platform experiences.
Throughout the subsequent years, JetBrains kept enhancing KMM with better tooling, support for iOS development, and a constantly growing ecosystem of libraries and frameworks. The Kotlin 1.4 release in 2020 further nailed up the status of KMM in the mobile arena by providing improvements to the Kotlin compiler, multiplatform support, and closer integration with IDEs such as Android Studio and IntelliJ IDEA. The community of Kotlin grew, and the contribution to the growth and maturity of KMM is also due to plugins, libraries, and third-party tools.
By 2021, KMM had moved from being experimental into an Alpha phase, meaning it was already fit for wider adoption. As performance continued to improve, so did the developer experience and stability; KMM started to receive attention from companies and developers seeking productive cross-platform solutions. Particularly, it became alluring for teams that already had experience working with Kotlin because they could reuse codebases and existing knowledge.
Nowadays, Kotlin Multiplatform Mobile is an effective and flexible means of performing cross-platform mobile development. Thanks to ongoing investment by JetBrains and the community, enhancements continually arrive to further sweeten this combination. With growing production adoptions, KMM's future seems bright. KMM speaks to just how far this realm of cross-platform development will take us, fusing code reusability with the imperatives of native performance and experience on mobile platforms.
One of the big challenges in mobile app development is that every developer or organization has to support multiple platforms, primarily Android and iOS. Conventional wisdom has been to develop, maintain, and update separate codebases for each of them, which is an extremely cumbersome and expensive affair because it demands specialized knowledge in Android and iOS development. This, in turn, results in greater cost, longer development cycles, and introduces various complications related to feature parity and consistency of user experience across the platforms.
Currently available cross-platform development frameworks, including React Native, Flutter, and Xamarin, seek to avoid these issues by making a single code run on multiple platforms. Yet most of these solutions are not free from certain drawbacks: limited access to native APIs, performance loss, and an extra hassle of learning a new language or framework. Most of the frameworks also enforce developers to rely on third-party tools and plugins that may not be updated every moment or capable of supporting all platform-specific features. This, in turn, can make such solutions fall short of being fully native experiences, which users expect. In some cases, where high performance or complex applications require high performance or complexity, such solutions cannot meet the expectations created by an all-native experience.
Therefore, with these challenges, what is seriously needed is a solution to offer, proficiently, code sharing on various platforms without any tradeoff between performance and user experience. In this respect, what developers need is support for code reuse that gives them the possibility to utilize their existing knowledge and expertise while providing them the flexibility to enable platform-specific capabilities where they are necessary.
Kotlin Multiplatform Mobile (KMM) attempts to fix the problem by offering another approach to cross-platform mobile development. KMM enables developers to share the core logic and business modules of an application between Android and iOS while maintaining platform-specific code separate, usually to handle native UI and other unique features. In such a way, the approach is able to support substantial code reuse, reduce time and cost during the development process, and maintain a high-quality native user experience. However, KMM also faces its own set of challenges in reaching mainstream status for cross-platform mobile development, including further improvements of tooling, maturation of the ecosystem, and community adoption.
The original idea behind KMM was some sort of segregation into shared code and platform-specific code. Shared code, as the name suggests, normally would include pure Kotlin-business logic, data models, and other non-UI components which could be shared across Android and iOS platforms. Platform-specific code, usually UI components and device-specific functionalities, remains segregated and is written in native languages: Kotlin for Android, Swift or Objective C for iOS. This layer of separation allows the developers to provide the best possible user experience, leveraging the capabilities unique to each platform.
KMM relies on the Kotlin Multiplatform Gradle Plugin as the core tool to manage project dependencies, compilation, and packaging. The Gradle plugin allows a developer to specify shared modules for compilation to multiple target platforms. The plugin also supports the possibility of specifying additional platform-specific source sets, allowing a developer to write platform-dependent code under the same project structure. As a result of this tight integration with Gradle, it is easier for an Android developer to learn.
KMM for iOS development integrates with Xcode, Apple's development environment. Developers can create shared Kotlin modules and link them as dependencies inside an Xcode project. Moreover, KMM provides support for tools like CocoaPods integration for managing dependencies and facilitates generating Objective-C or Swift-compatible binaries, making using Kotlin code in existing iOS projects easy.
KMM is backed by an ever-growing set of libraries and frameworks that will ease development, such as Ktor for networking, SQLDelight for database management, and Kotlinx.serialization for data serialization. These are designed to share seamlessly across platforms, hence further enhancing code reuse. The use of these libraries allows the developer to write the majority of application logic only once, with reliance on the platform-specific libraries for UI and device-specific features.
Key use cases of KMM are the development of business-logic-intensive mobile applications. That means very basic logic, like authentication, data storage, networking, or even business rules of applications, can be shared between the platforms with the help of KMM. That kind of application would utilize KMM for core functionality, such as user authentication, transaction processing, and data synchronization, within the shared library, and native user interfaces would be created for each target platform. There is fair behavior across platforms, and it greatly reduces code duplication, which decreases cost and effort.
KMM has a specific advantage for the teams already working in Kotlin, especially those who previously have been developing an Android app. By using KMM, the team can easily begin developing cross-platform apps because prior Kotlin experience can be utilized without needing to adopt new programming languages and frameworks. This makes extension of the already existing Android app to iOS far easier. With this, one can gradually adopt the cross-platform development while guaranteeing the same quality and performance of a native app.
Another good example of the practical usage of KMM is the development of libraries/Sdks for both Android and iOS. Companies working on analytics, payment processing libraries, authentication services, and so on will benefit from the usage of KMM by sharing a codebase between platforms, thus guaranteeing feature parity with minimum maintenance overhead. In such a way, this approach accelerates mobile SDK development, increases the speed of updates, and provides consistency in functionality across the board.
Besides, KMM can be used to enable startups and small development teams to implement cross-platform MVPs quickly and without wasting much time. By sharing common core logic and concerns, the KMM will further enable them to save precious time by spending their time and resources on reinventing the wheel when needed. Speed up the time to market, reduce the costs of development, and with ease allow changes upon early user feedback.
While KMM does indeed hold so much promise in its approach to cross-platform mobile development, it is burdened with a number of challenges and limitations that may hinder its wide adoption and effectiveness.
This is mostly about the relative immaturity of the KMM ecosystem. The problems relate to the fact that, compared to many established cross-platform frameworks like React Native or Flutter, KMM still lacks extensive libraries and tools that have matured over time. This simply means it might be required that certain functionalities have to be developed from scratch or adapted from some other libraries, which makes the development slower and more complex.
Another limitation would be that one needs to know both Android and iOS development environments. Even though KMM allows developers to share core logic, platform-specific code for the UI and other native features still has to be written. Knowledge in both Kotlin for Android and Swift or Objective-C for iOS may be required, possibly putting a steep curve in front of teams lacking experience in both ecosystems.
Another place where challenges arise is tooling support. While JetBrains and the community continuously improve the KMM tooling, some functionality-like debugging and testing of shared code across platforms-is still evolving. These limitations sometimes result in a less streamlined development experience.
Performance for KMM applications, while usually good, may also not be on par in very specific performance-optimized platform code scenarios, such as gaming or heavy graphics processing.
Thus, the future looks bright, and KMM continues to gain traction with developers and organizations looking for effective solutions for cross-platform mobile development. With JetBrains actively investing in the development of KMM, this framework is destined to see even more developments in the areas of tooling, performance, and ecosystem support.
It is also one of the big focus areas: improving the development experience by enhancements in IDE integration, debugging, testing, and better documentation that will make the development process smoother and friendlier for any level developer. It's expected that expansion will also happen in the library ecosystem: more third-party libraries will be ported or specifically developed for KMM, reducing the custom implementations and speeding up the development.
In addition, KMM is poised to be one of the preferred choices for teams experienced with Kotlin due to its pragmatic approach toward code sharing with native performance. The adoption of KMM is going to continue in each and every organization looking at finding a balanced approach toward cross-platform development, leveraging shared code and platform-specific capabilities to reduce development costs and time-to-market without sacrificing user experience.
In general, KMM is supposed to play a great role in the future of mobile application development, presenting a flexible, performant, developer-friendly solution for cross-platform application development.
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