The run Loop for iOS development

<span id="Label3"></p><p><p><strong>1</strong> <strong>, overview</strong></p></p><p><p>(1) Run Loop provides a mechanism for executing code asynchronously and cannot perform tasks in Parallel.</p></p><p><p>(2) in the main queue, main run loop works directly with the execution of the task, handling UI events, timers, and other kernel-related Events.</p></p><p><p>(3) The main purpose of the run loop is to ensure that the thread that executes the program is not terminated by the System.</p></p><p><p><strong>Run Loop</strong> <strong>characteristics of the Work:</strong></p></p><p><p>(1) when an event occurs, the Run Loop notifies the application to respond based on the specific event Type.</p></p><p><p>(2) when no event occurs, the Run loop goes into hibernation to save Power.</p></p><p><p>(3) when the event occurs again, the Run loop is woken up to handle the Event.</p></p><p><p><strong>the main thread and other threads in the</strong> <strong>Run Loop</strong> <strong>:</strong></p></p><p><p>The main thread of the iOS program is already configured with Run loop by default, and other threads do not have the run loop set by Default.</p></p><p><p>Typically in development, Runloop are rarely actively created, and events are usually added to Runloop.</p></p><p><p><strong>Loop</strong> <strong>:</strong></p></p><p><p></p></p><p><p><strong>2</strong> <strong>,</strong> <strong>uiapplication</strong> <strong>in the</strong> <strong>Run Loop</strong></p></p><p><p><strong></strong></p></p><p><p><strong>3</strong> <strong>,</strong> <strong>circular references in multi-threading</strong></p></p><p><p>A circular reference can be caused if the Self object holds a reference to an operand, and the manipulation object directly accesses Self.</p></p><p><p>Using self in a manipulation object alone does not cause circular references.</p></p><p><p>Note: not available at this time (weakself)</p></p><p><p><strong>4</strong> <strong>, resource sharing in multiple threads</strong></p></p><p><p>Many of the problems in concurrent programming are rooted in accessing shared resources in multiple THREADS. A resource can be a property, an object, a network device, or a file.</p></p><p><p>Any shared resource in multiple threads can be a potential conflict point and must be carefully designed to prevent this conflict from Occurring.</p></p><p><p><strong>Resource Sharing Examples:</strong></p></p><p><p><strong></strong></p></p><p><p><strong>5</strong> <strong>,</strong> <strong>Mutual exclusion Lock</strong> <strong>(@synchronized)</strong></p></p><p><p>Mutual exclusion Lock Use note:</p></p><p><p>(1) plus mutex, add mutex in "read" "write" scope of shared resource</p></p><p><p>(2) to make the range of the lock as small as possible!</p></p><p><p>(3) resource looting doing the simple thing is to use the mutex lock @synchronized</p></p><p><p>(4) the use of mutual exclusion lock, will be slow, the cost of mutual exclusion lock is very high!</p></p><p><p></p></p><p><p>Plus a mutex allows a resource to be accessed only by one thread at a time, and only when the resource is exhausted by the Thread.</p></p><p><p>Mutex usage:</p></p><p><p>@synchronized (self) {</p></p><p><p>Threading Operations</p></p><p><p>}</p></p><p><p>For example:</p></p><p><p>@interface Mjviewcontroller ()</p></p><p><p>@property (weak, nonatomic) iboutlet uitextview *infotext;</p></p><p><p>The number of votes, <strong>if the use of atomic lock, just on the basis of mutual exclusion lock to</strong> <strong></strong> <strong>Change</strong> The following nonatomic <strong>atomic</strong> <strong>can</strong> be</p></p><p><p>@property (nonatomic, Assign) Nsinteger tickets;</p></p><p><p>@end</p></p><p><p></p></p><p><p>@implementation Mjviewcontroller</p></p><p><p></p></p><p><p>-(void) Viewdidload</p></p><p><p>{</p></p><p><p>[super viewdidload];</p></p><p><p>}</p></p><p><p></p></p><p><p>The circulation of the tickets has been sold out so far</p></p><p><p>-(void) dosaleloop: (nsstring *) opname</p></p><p><p>{</p></p><p><p>All threads are allowed to circulate and sell Tickets.</p></p><p><p>While (YES) {</p></p><p><p></p></p><p><p>@synchronized (self) {</p></p><p><p>If (self.tickets > 0) {</p></p><p><p>--self.tickets;</p></p><p><p></p></p><p><p>NSLog (@ "number of votes left%d-%@-%@", self.tickets, opname, [nsthread currentthread]);</p></p><p><p>} else {</p></p><p><p>Break</p></p><p><p>}</p></p><p><p>}</p></p><p><p>//-----------------------------------------</p></p><p><p>Simulated hibernation, unrelated to resource looting, not in a lock.</p></p><p><p>If ([opname isequaltostring:@ "OP 1"]) {</p></p><p><p>[nsthread sleepfortimeinterval:1.0f];</p></p><p><p>} else {</p></p><p><p>[nsthread sleepfortimeinterval:0.3f];</p></p><p><p>}</p></p><p><p>}</p></p><p><p>}</p></p><p><p></p></p><p><p>#pragma mark Mock multiplayer sell ticket</p></p><p><p>#pragma Mark Gcd realizes</p></p><p><p></p></p><p><p>-(ibaction) dosale: (id) Sender</p></p><p><p>{</p></p><p><p>Do multi-threaded start, never trust the results of a run</p></p><p><p>Self.tickets = 20;</p></p><p><p></p></p><p><p>1. Queue</p></p><p><p>dispatch_queue_t q = dispatch_queue_create ("sale", dispatch_queue_concurrent);</p></p><p><p></p></p><p><p>2. Add a task</p></p><p><p>Dispatch_async (q, ^{</p></p><p><p>[self dosaleloop:@ "OP 1"];</p></p><p><p>});</p></p><p><p></p></p><p><p>Dispatch_async (q, ^{</p></p><p><p>[self dosaleloop:@ "OP 2"];</p></p><p><p>});</p></p><p><p></p></p><p><p>Dispatch_async (q, ^{</p></p><p><p>[self dosaleloop:@ "OP 3"];</p></p><p><p>});</p></p><p><p></p></p><p><p>Dispatch_async (q, ^{</p></p><p><p>[self dosaleloop:@ "OP 4"];</p></p><p><p>});</p></p><p><p>}</p></p><p><p></p></p><p><p>@end</p></p><p><p>Note: There is also a lock feature in ios, atomic lock-a read-write lock (128-bit spin lock), which also consumes performance.</p></p><p><p>The atomic lock only protects the data when it is written, while reading is not responsible.</p></p><p><p>For the resources to write, it is important to protect the correctness of the write data, or the accuracy of the reads!</p></p><p><p>If you just develop a single-write multi-read feature, you only need to use an atomic lock.</p></p><p><p><strong>@synchronized</strong> <strong>performance consumption is very large, Apple is not recommended for official Use. </strong></p></p><p><p><strong>In the actual development, do not Rob resources!</strong></p></p><p><p>The main purpose of concurrent programming is to improve performance, to allow more code to run concurrently, to achieve concurrency and improve overall performance!</p></p><p><p>Mobile phone development is the most important is smooth, parallel, as for the resource Rob function development is a service-side category!</p></p><p><p></p></p><p><p>The run Loop for iOS development</p></p></span>