GCD applications and Other methods

1.GCD Application Single-case mode

Static dispatch_once_t Oncetoken;
Dispatch_once (&oncetoken, ^{

NSLog (@ "Execute once%@", [Nsthread CurrentThread]);

});

2. Deferred operation
1.
NSLog (@ "Start execution");

[Self performselector: @selector (handleaction) Withobject:nil afterdelay:0];

2.

Dispatch_time_now from now on.
Delayinseconds delay for a few seconds

dispatch_time_t time = Dispatch_time (Dispatch_time_now, (int64_t) (2 * nsec_per_sec));

When dispatch_time_t

Dispatch_after (Time, Dispatch_get_main_queue (), ^{

NSLog (@ "%@", [Nsthread CurrentThread]);

});

3. Scheduling Group

Create a dispatch group
dispatch_group_t group = Dispatch_group_create ();
Get Global Queue
dispatch_queue_t queue = dispatch_get_global_queue (0, 0);
Asynchronous requests for dispatch groups
Dispatch_group_async (group, queue, ^{

[Nsthread Sleepfortimeinterval:2];
NSLog (@ "Download first picture");
});
Dispatch_group_async (group, queue, ^{
[Nsthread Sleepfortimeinterval:3];

NSLog (@ "Download second picture");
});
Dispatch_group_async (group, queue, ^{
[Nsthread sleepfortimeinterval:1];

NSLog (@ "Download the third picture");
});
Dispatch_group_async (group, queue, ^{
[Nsthread Sleepfortimeinterval:5];

NSLog (@ "Download fourth picture");
});
Notify notification, called when all asynchronous requests are complete dispatch_group_notify
Dispatch_group_notify (group, queue, ^{
NSLog (@ "Update UI");
});

4. Second way of scheduling group

Create a dispatch group
dispatch_group_t group = Dispatch_group_create ();
Get Global Queue
dispatch_queue_t queue = dispatch_get_global_queue (0, 0);

Enter queue
Dispatch_group_enter (group);
Dispatch_async (Queue, ^{

[Nsthread Sleepfortimeinterval:2];
NSLog (@ "Download first picture");

Leave the queue
Dispatch_group_leave (group);
});

Dispatch_group_enter (group);
Dispatch_async (Queue, ^{

[Nsthread sleepfortimeinterval:1];
NSLog (@ "Download er map");

Dispatch_group_leave (group);
});

Dispatch_group_enter (group);
Dispatch_async (Queue, ^{

[Nsthread Sleepfortimeinterval:3];
NSLog (@ "Download san map");

Dispatch_group_leave (group);
});

Wait for the dispatch queue wait equals a blocking state after the last asynchronous process executes, the update UI executes
Dispatch_group_wait (group, dispatch_time_forever);

NSLog (@ "Update UI");

5. Interrupt Operation

Dispatch_barrier_async must be a custom queue
The concurrent queue specified here should be created by itself through the dispatch_queue_create function. If you pass a serial queue or a global concurrency queue, this function is equivalent to the Dispatch_async function.

dispatch_queue_t queue = dispatch_queue_create ("COM.BLOGCN", dispatch_queue_concurrent); Dispatch_get_global_queue (0, 0);

Dispatch_async (Queue, ^{
[Nsthread sleepfortimeinterval:1];
NSLog (@ "1");
});

Dispatch_async (Queue, ^{
[Nsthread Sleepfortimeinterval:3];

NSLog (@ "2");
});
Dispatch_async (Queue, ^{

[Nsthread Sleepfortimeinterval:2];

NSLog (@ "3");
});

Interrupt Operation Dispatch_barrier_async
Dispatch_barrier_async (Queue, ^{
NSLog (@ "--------");
[Nsthread sleepfortimeinterval:1];

});

Dispatch_async (Queue, ^{

[Nsthread sleepfortimeinterval:1];
NSLog (@ "4");
});
Dispatch_async (Queue, ^{
NSLog (@ "5");
});

6. Traverse

Traversal operations
dispatch_queue_t queue = dispatch_get_global_queue (0, 0);
Number of iterations traversal
Dispatch_apply (5, queue, ^ (size_t i) {
NSLog (@ "%@", @ (i));
});

GCD applications and Other methods