Why should I choose GCD over NSOperation and blocks for high-level applications?

Question

Apple\'s Grand Central Dispatch reference says:

\"...if your application needs to operate at the Unix level of the system—for example, if it needs t

Answer 1

• Prefer GCD where task is not much complex and optimum CPU performance is required.
• Prefer NSOperationQueue where task is complex and requires canceling or suspending a block and dependency management.

GCD is a lightweight way to represent units of work that are going to be executed concurrently. You don’t schedule these units of work; the system takes care of scheduling for you. Adding dependency among blocks can be a headache. Canceling or suspending a block creates extra work for you as a developer!

NSOperation and NSOperationQueue add a little extra overhead compared to GCD, but you can add dependency among various operations. You can re-use, cancel or suspend operations. NSOperation is compatible with Key-Value Observation (KVO); for example, you can have an NSOperation start running by listening to NSNotificationCenter.

For detailed explanation, refer this question: NSOperation vs Grand Central Dispatch