kotlin-patterns

Use non-nullable types by default, safe-call operators (?.), and the Elvis operator (?:) for defaults. Avoid force-unwrapping with !! since it throws NPE; instead throw descriptive exceptions or return nullable types from lookups.

Wrap parallel work in coroutineScope and launch child jobs with async, then combine results with await. Use supervisorScope when child failures should not cancel siblings, and never use GlobalScope for application work.

Use sealed classes for restricted hierarchies with shared state, such as a Result type with Success, Failure, and Loading variants. Use sealed interfaces when implementations need multiple inheritance or are spread across class hierarchies, like API error types.

let transforms a nullable or scoped result, apply configures an object and returns it, also adds side effects while returning the object, and run or with execute a block on a receiver returning the result. Avoid nesting scope functions; chain safe calls instead.

Yes, Flow supports debounce, distinctUntilChanged, filter, and mapLatest operators for search pipelines, plus catch for error handling. A typical pattern debounces query input by 300ms, filters short queries, and emits empty lists on errors.

Sequences add overhead for small collections or single operations, so use them only for large collections with multiple chained operations like filter plus map plus take. For simple one-pass operations on small lists, eager collection operations are cheaper.