Review Knowledge Points: GCD multithreading

The foundation of GCD

1 #pragmaMark-Create a serial queue using GCD2     //First: System-provided methods for creating a serial queue3     //in real development if you need to create a serial queue, it is more customary to use this4 //dispatch_queue_t queue = Dispatch_get_main_queue ();5 6 #pragmaMark-use GCD to create a parallel queue7     //the first type: System8     //parameter 1: Priority (four, no significant difference)9     //Parameter 2: System reserved wordTen //dispatch_queue_t queue = dispatch_get_global_queue (dispatch_queue_priority_background, 0); One  A #pragmaMark-Create child threads using GCD parallel queue -     //parameter 1: queue name -     //parameter 2:block//dispatch_async (queue, ^{ the //NSLog (@ "main1 =%@", [Nsthread Mainthread]); - //NSLog (@ "current1 =%@", [Nsthread CurrentThread]); - //    }); - //dispatch_async (queue, ^{ + //NSLog (@ "main2 =%@", [Nsthread Mainthread]); - //NSLog (@ "Current2 =%@", [Nsthread CurrentThread]); + //    }); A //dispatch_async (queue, ^{ at //NSLog (@ "main3 =%@", [Nsthread Mainthread]); - //NSLog (@ "Current3 =%@", [Nsthread CurrentThread]); - //    }); - //....  Create a N -  - #pragmaMark--a few seconds to do everything. in //Dispatch_after (Dispatch_time (Dispatch_time_now, (int64_t) (3.0 * nsec_per_sec)), Dispatch_get_main_queue (), ^{  - //NSLog (@ "3 seconds"); to //    }); +  - #pragmaMark-Repeat to add multiple tasks like a queue the //dispatch_queue_t queue = dispatch_queue_create (0, dispatch_queue_concurrent); *     //First parameter: Number of additions $     //second parameter: queuePanax Notoginseng     //Third parameter: Block - //dispatch_apply (+, queue, ^ (size_t index) { the //NSLog (@ "%ld", index); + //    }); A  the #pragmaMark-Group + //    //Create a group - //dispatch_group_t group = Dispatch_group_create (); $ //    //Create a queue $ //dispatch_queue_t queue = dispatch_queue_create (0, dispatch_queue_concurrent); - //    //Create Task 1: - //Dispatch_group_async (Group, queue, ^{ the //NSLog (@ "I am 1"); - //    });Wuyi //    //Create Task 2: the //Dispatch_group_async (Group, queue, ^{ - //NSLog (@ "I am 2"); Wu //    }); - //....  Create a N About  $ //    //{So this function code must be placed after all tasks} to listen for the condition that the task is known to execute - //dispatch_group_notify (Group, queue, ^{ - //NSLog (@ "I am notify"); - //    }); A  + #pragmaMark-Serial in concurrency (Wolf in sheep's clothing) the //    //queue created by serial - //    //dispatch_queue_serial Sequential Execution $ //    //dispatch_queue_concurrent unordered Execution the //dispatch_queue_t queue = dispatch_queue_create (0, dispatch_queue_concurrent); the //dispatch_async (queue, ^{ the //NSLog (@ "Test 1"); the //    }); - //dispatch_async (queue, ^{ in //NSLog (@ "Test 2"); the //    }); the //....  Create a N

Code Show:

1 #import "ViewController.h"2 3 @interfaceViewcontroller ()4 ///Create a ImageView5@property (nonatomic,strong) Uiimageview *Imgview;6 ///create a data to receive7@property (nonatomic,strong) NSData *ImageData;8 9 @endTen  One @implementationViewcontroller A  -- (void) Viewdidload { - [Super Viewdidload]; the     //additional setup after loading the view, typically from a nib. -     //Add ImageView to the view -Self.imgview =[[Uiimageview alloc] Initwithframe:[uiscreen mainscreen].bounds]; -Self.imgView.backgroundColor =[Uicolor Cyancolor]; + [Self.view AddSubview:self.imgView]; -      + [self datahandle]; A } at #pragmaMark-Parsing data -- (void) Datahandle { -__weaktypeof(self) weakself =Self ; -     //Create a child thread to request data in a child thread -Dispatch_async (Dispatch_queue_create (0, dispatch_queue_concurrent), ^{ -Nsurl *url = [Nsurl urlwithstring:@"http://pic.58pic.com/58pic/13/11/15/83b58PICXf4_1024.jpg"]; in         //Receive Data -Weakself.imagedata =[NSData Datawithcontentsofurl:url]; to         //return to main thread refresh UI +Dispatch_async (Dispatch_get_main_queue (), ^{ -             //Pass Value theWeakSelf.imgView.image =[UIImage ImageWithData:self.imageData]; *         }); $     });Panax Notoginseng      - } the  + @end

Review Knowledge Points: GCD multithreading