Basics of multithreaded Programming for iOS

Last Update:2015-10-19 Source: Internet

Author: User

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Multithreading is a way to address the main thread being blocked and to improve Efficiency. First of all we have to learn multithreaded programming to see how it has several ways: <ol> <ol> <li>Nsthread</li> <li>Nsoperation</li> <li>Grand centeral Dispatch </li> </ol> </ol>Let's see how nsthread is created:<pre class="brush:cpp;toolbar: true; auto-links: false;"><pre class="brush:cpp;toolbar:true; auto-links:false;">nsthread *thread = [[nsthread Alloc]initwithtarget:self selector: @selector (btnsum:) object:nil]; //through iniit Creating nsthread requires manual threading [thread start]; [thread cancel]; //the second open and automatic execution btnSum is a way to write for yourself [nsthread detachnewthreadselector: @selector (btnsum:) totarget:self withobject:nil]; </pre></pre><pre class="brush:cpp;toolbar: true; auto-links: false;"><pre class="brush:cpp;toolbar:true; auto-links:false;">- (void) btnsum: (uibutton *) sender { long sum = 0; for (long i = 0; i < 10; i ++) { sum += i; NSLog (@ "number %ld current thred : %@ %@", Sum,[nsthread currentthread ],[nsoperationqueue currentqueue]); } } </pre></pre>Use Nsthread or directly from the NSObject class method performselectorinbackground:withobject: to create a thread. If you choose thread to implement multi-threading, then Nsthread is the preferred way to use the official recommendation Nsoperation<pre class="brush:cpp;toolbar: true; auto-links: false;"><pre class="brush:cpp;toolbar:true; auto-links:false;">/** nsoperationqueue thread queue */// 1.nsinvocationoperation Operation nsinvocationoperation *iop =[[nsinvocationoperation alloc]initwithtarget:self selector: @selector (btnSum:) object:nil ]; //operation is not executable and requires a queue to be called [[ nsoperationqueue mainqueue] addoperation:iop]; //2. nsblockoperation nsblockoperation *bop = [[ Nsblockoperation alloc]init]; //adding actions as a block of code [bOP addexecutionblock:^{ [self btnsum:nil]; }]; //added to Thread queue [self.operationqueue addoperation:bop]; </pre></pre>To create a simple nsoperation object, rewrite the Getter method directly <pre class="brush:cpp;toolbar: true; auto-links: false;"><pre class="brush:cpp;toolbar: true; auto-links: false;">-(nsoperationqueue *) operationqueue{if (!_operationqueue) {_operationqueue = [[nsoperationqueue alloc]init]; [_operationqueue setname:@ "queue"]; } return _operationqueue;}</pre></pre><pre class="brush:cpp;toolbar: true; auto-links: false;">nsblockoperation creation method, You can use the convenient constructor, directly add block nsblockoperation *bop = [nsblockoperation blockoperationwithblock:^{ for (int i = 0; i < 100; i ++) { nslog (@ "%d, Current thread:::%@", i,[nsthread currentthread]); } }]; nsblockoperation *aop = [NSBlockOperation blockOperationWithBlock:^{ for (int i = 0; i < 100; i ++) { nslog (@ "%d, Current thread:::%@", i,[nsthread currentthread]); } }]; nsblockoperation *cop = [nsblockoperation blockoperationwithblock:^{ for (int i = 0; i < 100; i ++) { nslog (@ "%d, Current thread 333333333:::%@", i,[nsthread currentthread] ); } }]; //add to primary queue [[nsoperationqueue mainqueue] addoperation:bop]; [[ Nsoperationqueue mainqueue] addoperation:cop];//custom Queue self.operation = [[nsoperationqueue alloc]init]; //setting the maximum number of concurrent Self.operation.maxconcurrentoperationcount = 1;//only perform one operation at the same continuous time// self.operation.maxconcurrentoperationcount = 4; [self Performselectorinbackground: @selector (PRINTNUmber:) withobject:@ "NSOBJECT"];&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;[SELF.OPERATION&NBSP;ADDOPERATION:AOP ]; [self.operation addoperation:cop];</pre> GCD <pre class="brush:cpp;toolbar: true; auto-links: false;">/**gcd Central distribution mechanism Grand Central Dispatch function-based, use distribution queue fifo*/ //1. Main thread queue:: equivalent to [nsoperationqueue mainqueue] //2. global thread queue background queue parallel //3. Custom thread Queue DISPATCH_QUEUE_SERIAL serial// DISPATCH_QUEUE_CONCURRENT Parallel /* //create a custom queue, default to serial (so add a priority to the East::D Ispatch_queue_priority_default) dispatch_queue_t myqueue = dispatch_queue_create (" Com.liulei.www.myQueue ", dispatch_queue_priority_default); //serial queue // dispatch_async (queue, Execution Block) asynchronous // dispatch_sync (queue, Execute block) sync dispatch_async (myqueue, ^{ [self printnumber:@ "GCD"]; [self printnumber:@ "GCD1"]; }); dispatch_async (myqueue, ^{ [self printnumber:@ "GCD2"]; }); */ /*//parallel Queue dispatch_queue_t conqueue = dispatch_ Queue_create ("conqueue", dispatch_queue_concurrent); // A bolck in serial dispatch_async (conqueue, ^{ //sequential Execution [self printnumber:@ "G1"]; [self printnumber:@ "G2"]; [ self printnumber:@ "G3"]; //parallel Execution Dispatch_async (conqueue, ^{ [self printnumber:@ "G4"]; }); dispatch_ Async (conqueue, ^{ [self printnumber:@ "G5"]; }); */ //dispatch_after .. Delay operation</pre>Since said multi-threaded development, will inevitably be in the multi-threaded communication; Using some of the NSObject 's class methods, it can be easily done. (nsobject built-in methods to create Threads)Do things in the main thread of the application: -(void) performselectoronmainthread: (SEL) aselector withobject: (id) arg waituntildone: (BOOL) wait-(void) performselectoronmainthread: (SEL) aselector withobject: (id) arg waituntildone: (BOOL) wait modes: (nsarray *) ArrayTo do something in the specified thread: -(void) performselector: (SEL) aselector onthread: (nsthread *) thr withobject: (id) arg waituntildone: (BOOL) wait-(void) performselector: (SEL) aselector onthread: (nsthread *) thr withobject: (id) arg waituntildone: (BOOL) wait modes: ( Nsarray *) Array Do things in the current thread: Invokes a method of the receiver on the current thread, using the default mode after a delay. -(void) performselector: (SEL) aselector withobject: (id) anargument afterdelay: (nstimeinterval) delayPerformSelector:withObject:afterDelay:inModes:Cancels a message sent to the current thread Cancelpreviousperformrequestswithtarget:CancelPreviousPerformRequestsWithTarget:selector:object:such as when we download data in a thread, after the download is complete to notify the main thread update interface, etc., You can use the following interface:- [self performselectoronmainthread: @selector (updateUI) withobject:nil waituntildone:no]; For example, when the download is complete, notify the main thread (ui Thread) so that the app can do other work Basics of multithreaded Programming for iOS

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