Plan an Objective-C to Swift migration
Move incrementally while keeping behavior easy to verify.
Start at a small boundary
Choose a well-understood type or module with clear inputs and outputs. Keep the app building throughout the migration. You can use Objective-C and Swift together while changing one part at a time.
Review the model
Reconsider nullability, value versus reference semantics, and collection element types. A mechanically translated Objective-C object graph may miss opportunities for clearer Swift models. Preserve observable behavior before redesigning it.
Preserve error and callback contracts
A completion handler can call back on a particular queue, permit cancellation, or deliver multiple results. Mapping it to async requires understanding those guarantees. Document error handling rather than replacing failures with defaults.
Validate on the target platform
Compile and run in the real application environment. Test boundary cases: nil, empty collections, invalid input, interrupted work, and interoperability with remaining Objective-C callers. Browser snippets are useful experiments, but cannot validate an entire app.