Multi-Threading Focus summary for iOS development

1. Asynchronous concurrent queue: it is used more


- (void) Touchesbegan: (Nsset *) touches withevent: (Uievent *)Event{    //Dispatch_sync: Synchronous, without the ability to open threads//Dispatch_async: Asynchronous, with the ability to open threads//concurrent queues: Multiple tasks can be executed concurrently//serial queue: Once a task is finished, the next task is executed//get a global concurrent queuedispatch_queue_t queue = Dispatch_get_global_queue (Dispatch_queue_priority_default,0); //Add a task to the global queue to execute asynchronouslyDispatch_async (Queue, ^{NSLog (@"-----Download Image 1---%@", [Nsthread CurrentThread]);    }); Dispatch_async (Queue,^{NSLog (@"-----Download Image 2---%@", [Nsthread CurrentThread]);    }); Dispatch_async (Queue,^{NSLog (@"-----Download Image 3---%@", [Nsthread CurrentThread]);    }); Dispatch_async (Queue,^{NSLog (@"-----Download Image 4---%@", [Nsthread CurrentThread]);    }); Dispatch_async (Queue,^{NSLog (@"-----Download Image 5---%@", [Nsthread CurrentThread]); });}

2. Download the image asynchronously and then go back to the main line loads load image Refresh UI

- (void) Touchesbegan: (Nsset *) touches withevent: (Uievent *)Event{nsoperationqueue*queue =[[Nsoperationqueue alloc] init]; [Queue Addoperationwithblock:^{        //1. Download images asynchronouslyNsurl *url = [Nsurl urlwithstring:@"http://d.hiphotos.baidu.com/image/pic/item/37d3d539b6003af3290eaf5d362ac65c1038b652.jpg"]; NSData*data =[NSData Datawithcontentsofurl:url]; UIImage*image =[UIImage Imagewithdata:data]; //2. Back to the main thread, display the picture//[Self performselectoronmainthread:<# (SEL) #> withobject:<# (ID) #> waituntildone:<# (BOOL) #>];< /c8>//Dispatch_async (Dispatch_get_main_queue (), ^{//            //        });[[Nsoperationqueue Mainqueue] addoperationwithblock:^{self.imageView.image=image;    }]; }];}

3. Adding dependencies between thread tasks

- (void) dependency{/** Assume A, B, c three operations, requirements: 1.3 operations are executed asynchronously 2. Operation C relies on Operation B 3. Operation B depends on operation a*/        //1. Create a queue (not a home row)Nsoperationqueue *queue =[[Nsoperationqueue alloc] init]; //2. Create 3 ActionsNsblockoperation *operationa = [Nsblockoperation blockoperationwithblock:^{NSLog (@"A1---%@", [Nsthread CurrentThread]);        }]; Nsblockoperation*OPERATIONB = [Nsblockoperation blockoperationwithblock:^{NSLog (@"B---%@", [Nsthread CurrentThread]);    }]; Nsblockoperation*operationc = [Nsblockoperation blockoperationwithblock:^{NSLog (@"C---%@", [Nsthread CurrentThread]);        }]; //Setting Dependencies[Operationb Adddependency:operationa];        [Operationc ADDDEPENDENCY:OPERATIONB]; //3. Add operations to the queue (automatically execute tasks asynchronously)[Queue Addoperation:operationc];    [Queue Addoperation:operationa]; [Queue addoperation:operationb];}

4. Maximum number of concurrent

Queue. Maxconcurrentoperationcount = 3;

5. Thread operations are generally canceled in memory warnings

[Queue cancelalloperations];//non-recoverable operation

[Queue Setsuspended:yes]; Pause All tasks in a queue

　　[Queue Setsuspended:no]; Recover All tasks in a queue

6. Thread safety: Need to lock @synchronize (self) {}

Create multiple threads First: Perform the same task (you need to assign an initial value to the ticket number to achieve the ticket sale)

-(void) Touchesbegan: (Nsset<uitouch *> *) touches withevent: (uievent *)event  {        [ Nsthread detachnewthreadselector: @selector (sellticket:) totarget:self withobject:@ "a" ];    [Nsthread detachnewthreadselector: @selector (sellticket:) totarget:self withobject:@ "b " ];    [Nsthread detachnewthreadselector: @selector (sellticket:) totarget:self withobject:@ "C " ];        }

Then lock the task implementation:

//the way to buy tickets requires encryption- (void) Sellticket: (NSString *) name { while(1) {@synchronized (self) {if(Self.ticketcount >0) {[Nsthread sleepfortimeinterval:0.3]; Self.ticketcount--; NSLog (@"%@---%d----%@---%d", [Nsthread currentthread],[nsthread Ismainthread],name,self.ticketcount); } Else {                return; }        }    }    }

Multi-Threading Focus summary for iOS development