seniorObjective-C
What is the difference between dispatch_async and dispatch_sync in system behavior?
Updated May 17, 2026
Short answer
dispatch_sync blocks current thread, while dispatch_async schedules work and returns immediately.
Deep explanation
sync submits a block and waits for completion, potentially causing deadlocks if misused. async schedules work on a queue without blocking. Misuse of sync on main queue is a common crash pattern.
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