iOS multithreaded Development gcd common usage

1- deferred execution

can schedule its thread (1), the home row

dispatch_queue_t queue= dispatch_get_main_queue ();

Dispatch_after (Dispatch_time (Dispatch_time_now, (int64_t) (5.0 * nsec_per_sec)), queue, ^{

NSLog (@ "Home row - deferred execution ------%@", [Nsthread CurrentThread]);

       });      

can schedule its threads (2), concurrent queues

1. Get global concurrent queues

dispatch_queue_t queue1= dispatch_get_global_queue (Dispatch_queue_priority_default, 0);

2. Calculate time for task execution

dispatch_time_t When=dispatch_time (Dispatch_time_now, (int64_t) (5.0 * nsec_per_sec));

3. The task in the queue will be executed at this point in time

Dispatch_after (when, queue1, ^{

NSLog (@ " concurrent Queue - deferred execution ------%@", [Nsthread CurrentThread]);

});

2. use dispatch_once Disposable code

Use the Dispatch_once function to ensure that a piece of code is executed only 1 times during program Operation

Static dispatch_once_t Oncetoken;

Dispatch_once (&oncetoken, ^{

Execute code only 1 times ( This is thread-safe by default )

});

The entire program runs, only once.

3. Queue Groups

The use of queue groups allows task 1 and Task 2 to be performed simultaneously, and when both tasks are completed, return to the main thread for interface display operations.

1. Create a queue group

dispatch_group_t group = dispatch_group_create();

2. Start a task

dispatch_group_async(group, dispatch_get_global_queue(0, 0), ^{ /c15>

});

3. Open a second task

dispatch_group_async(group, dispatch_get_global_queue(0, 0), ^{   

});

perform task 1\ Task 2 Operations simultaneously

4. All tasks in the group are completed, and then go back to the main thread to perform other operations

dispatch_group_notify(group,Dispatch_get_main_queue(), ^{

});

iOS multithreaded Development gcd common usage