kotlin-patterns

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

Wrap concurrent work in coroutineScope and launch child tasks with async, then combine results with await. Use supervisorScope when child failures should not cancel siblings, and never use GlobalScope since it breaks structured concurrency.

Use sealed classes for restricted hierarchies with shared state, such as a Result type with Success, Failure, and Loading. Use sealed interfaces when implementations need multiple inheritance, like modeling API error types with a common message property.

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 returning the result. Avoid nesting scope functions; chain safe calls instead.

Yes, Flow supports debounce, distinctUntilChanged, and mapLatest operators for search-as-you-type pipelines. Attach a catch operator to handle upstream errors and emit fallback values like empty lists.

Avoid sequences for small collections or single operations, since the iterator overhead outweighs lazy evaluation benefits. Sequences pay off for large collections with multiple chained operations like filter, map, and take.