What are the main differences in general code when developing with Kotlin Multiplatform?

When developing with Kotlin Multiplatform, the shared code has several differences from regular Kotlin code:

• Modularity and platform separation: shared code is written in special modules (commonMain), while platform-dependent code is in separate modules (androidMain, iosMain, etc.).

• Limited API: platform-specific libraries and APIs cannot be used directly in shared code. Instead, expect/actual mechanisms are used to declare interfaces and their implementations on specific platforms.

• Use of expect/actual: allows declaring expected functions or classes in shared code (expect), and implementing them separately for each platform (actual).

• Stricter restrictions on libraries: only multiplatform libraries or standard Kotlin libraries supporting MPP can be used in shared code.

Example of expect/actual usage:

// commonMain
expect fun getPlatformName(): String

// androidMain
actual fun getPlatformName() = "Android"

// iosMain
actual fun getPlatformName() = "iOS"

Thus, Kotlin Multiplatform shared code is aimed at maximum reusability but requires abstraction from platform-specific details.