There are 3 common multithreaded programming methods in iOS

1.NSThread

This approach requires management of the thread's lifecycle, synchronization, and locking issues, resulting in a certain performance overhead

2.NSOperation and the Nsoperationqueue

is based on OC implementation. Nsoperation encapsulates the actions that need to be performed in an object-oriented manner, and can then put this operation into a nsoperationqueue to execute asynchronously. Do not care about thread management, synchronization, and so on.

3.Grand centeral Dispatch

Short GCD,IOS4 only started to support, is the pure C language API. Since IPAD2 began, the Apple device has a dual-core CPU, in order to take full advantage of these 2 cores, GCD provides some new features to support multi-core parallel programming

A Nsthread instance represents a thread

One, gets the current thread

Nsthread *current = [Nsthread CurrentThread];

Second, get the main thread

1 Nsthread *main = [Nsthread mainthread];

2 NSLog (@ "Main thread:%@", main);

The printing results are:

2013-04-18 21:36:38.599 thread[7499:c07] Main thread: <nsthread:0x71434e0>{name = (null), num = 1}

Num equals the ID of the thread, and num for the main thread is 1.

Third, Nsthread the Creation

1. Dynamic Methods

-(ID) Initwithtarget: (ID) Target selector: (SEL) Selector object: (ID) argument;

* A new thread is created on line 2nd, and then the Start method is called on line 4th, and the thread starts with the run: Method of self and calls @ "MJ" as the method parameter

1//Initialize thread

2 Nsthread *thread = [[[Nsthread alloc] initwithtarget:self selector: @selector (run:) object:@ "MJ"] autorelease];

3//Open thread

4 [Thread start];

If run: The method is this:

1-(void) Run: (NSString *) string {

2 Nsthread *current = [Nsthread CurrentThread];

3 NSLog (@ "Run: Method-parameter:%@, current thread:%@", string, present);

4}

Printing results are:

2013-04-18 21:40:33.102 Thread[7542:3e13] Executed run: Method-parameter: MJ, current thread: <nsthread:0x889e8d0>{name = (null), num = 3}

It can be found that the NUM value of this thread is 3, indicating that it is not the main thread, and num of the main thread is 1

2. static Methods

+ (void) Detachnewthreadselector: (SEL) selector totarget: (ID) target withobject: (id) argument;

[Nsthread detachnewthreadselector: @selector (run:) totarget:self withobject:@ "MJ"];

After executing the above code, a new thread is started and the Self's Run: method is called on this thread, with @ "MJ" as the method parameter

3. implicitly creating Threads

[Self Performselectorinbackground: @selector (run:) withobject:@ "MJ"];

Creates a new thread implicitly, and calls Self's run: method on this thread, with @ "MJ" as the method parameter

Iv. pausing the current thread

[Nsthread Sleepfortimeinterval:2];

NSDate *date = [nsdate datewithtimeinterval:2 sincedate:[nsdate Date]];

[Nsthread Sleepuntildate:date];

Both of the above are pausing the current thread for 2 seconds

v. Other operations of the thread

1. perform actions on the specified thread

1 [Self performselector: @selector (run) onthread:thread Withobject:nil Waituntildone:yes];

* The above code means that the run method of self is called on thread

* The last yes means: The code above will block, and when the Run method finishes executing the thread, the code above will pass

2. perform actions on the main thread

[Self performselectoronmainthread: @selector (Run) Withobject:nil Waituntildone:yes];

Call the Run method of self on the main thread

3. performing actions on the current thread

[Self performselector: @selector (Run) Withobject:nil];

Call the Run method of self on the current thread

Vi. Advantages and disadvantages

1. Advantages: Nsthread is lighter than other multithreaded schemes and controls threading objects more intuitively

2. Cons: You need to manage the thread's life cycle, thread synchronization. Thread synchronization has a certain overhead in locking data