Безопасность null в общих моделях

A missing value is a top cause of app crashes. Kotlin's null safety lets shared models guard against it on both platforms.

A normal type can never hold null. Declaring a field as String guarantees it always has a real value.

Add a question mark to allow null. This marks a field as optional, so the compiler forces you to handle the empty case.

Use ?. to read a nullable field safely. If the value is null, the whole expression yields null instead of crashing.

The Elvis operator ?: supplies a default when the value is null, so downstream code always gets something usable.

Give a constructor parameter a default so callers can skip optional fields entirely while keeping the model non-null.

Once you confirm a value is not null, Kotlin smart casts it. Inside the check you use it as a plain non-null type.

The !! operator forces a value to non-null and crashes if it is null. Reach for safe calls and Elvis instead.

Mark a field nullable only when it truly can be absent. Clear types document your domain for both teams.

Null safety lives in commonMain, so Android and iOS inherit the same protection from the very same model. 🙂

Because nullability rules sit in shared code, neither app can accidentally treat an optional field as required.

Mark optional fields with ?, read them via safe calls and Elvis, and avoid !!, so shared models stay crash-safe on both apps.