IOSGCD Basic Usage

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#import "ViewController.h"

@interface viewcontroller ()

{

uiimageview *_view;

}

@end

@implementation Viewcontroller

-(void) viewdidload {

[superviewdidload];

// The Home row is a queue that is associated with the main thread, and the host column is a special queue that GCD provides, adding tasks to the main queue, Executes in the main thread. Note: Adding a task to the primary queue, either synchronously or asynchronously, does not create a thread.

//Dispatch_get_main_queue (); method to fetch to the home row

// turn on child thread call Test Method

[selfperformselectorinbackground:@selector(test) withobject:nil];

_view = [[uiimageviewalloc] Init];

_view. Frame = CGRectMake (0,0, self. ) View . bounds . size . width , - );

[self. View addsubview:_view];

}

-(void) test

{

dispatch_queue_t queue =dispatch_queue_create(" Concurrent Queue ",dispatch_queue_concurrent);

dispatch_async(queue, ^{

NSLog(@ "222 Curthread =%@", [nsthreadCurren TThread]);

});

dispatch_sync(queue, ^{

NSLog(@ "333 curethread =%@", [nsthreadCurrentt Hread]);

});

}

// The user taps the screen, downloads a picture from the network, and displays it to the interface.

-(void) Touchesbegan: ( Nsset *) touches withevent: (uievent *) Event

{

//1. Take global Queue

dispatch_queue_t queue =dispatch_get_global_queue( Dispatch_queue_priority_default,0);

// Add the task of downloading pictures to the parallel queue

dispatch_async(queue, ^{

NSLog(@ "1111:curthread =%@", [nsthread CurrentThread ]);

nsurl *url = [nsurlurlwithstring:@ "Http://h.hi Photos.baidu.com/image/pic/item/35a85edf8db1cb13966db40fde54564e92584ba2.jpg "];

nsdata *data = [nsdatadatawithcontentsofurl :url];

UIImage *image = [UIImageimagewithdata:d ATA];

// requires GCD to set the picture to be displayed in the main thread.

// benefits : in the main thread, you can use the resources in the child threads directly. Easy to use, intuitive.

// operation UI is executed in the main thread

dispatch_async(dispatch_get_main_queue(), ^{

_view. Image = image;

});

});

}

-(void) test11

{

//dispatch_queue_t queue = Dispatch_get_global_queue (< #long Identifier#>, < #unsigned long flags#>)

dispatch_queue_t queue =dispatch_queue_create("Concurrent queue" ,dispatch_queue_concurrent);

dispatch_async(queue, ^{

// do time-consuming operation

dispatch_async(dispatch_get_main_queue(), ^{

// operating UI interface

});

});

}

@end

IOSGCD Basic Usage