흔한 실수와 컴파일러 오류

expect/actual mistakes surface at compile time, never as silent runtime bugs. Learning the messages makes fixing them fast. 🛠️

The most common error is forgetting an actual for one target. The compiler says expected declaration has no actual for that platform.

Add the implementation in the right source set, like iosMain. Once every target has its actual, the build goes green.

If your actual changes the return type or parameters, the compiler reports that the actual does not match the expect. Align them exactly.

An implementation without the actual keyword looks like a separate function to the compiler, so it still complains the expect is unfulfilled.

Putting an actual in the wrong folder means a target still has no match. Each actual must sit in its platform's source set.

The actual has to share the exact package of its expect. A mismatched package leaves the expect looking unimplemented.

Using Android's Build or iOS UIDevice inside commonMain fails to resolve. Keep platform imports inside their own source sets only.

Declare default parameter values on the expect, not the actual. Repeating defaults on an actual triggers a compiler error.

Kotlin's errors usually name the exact target and member. Treat the message as a checklist and the fix is almost always obvious. 💡

Compile every target, not just Android. An iOS-only gap stays hidden until you build the iOS framework as well.

Spot the cause of the classic error.

You can now diagnose the usual expect/actual failures: a missing actual, a signature or package mismatch, or a platform import in common code. 🎉