Original address: http://www.cnblogs.com/wendingding/p/3805119.html
1, Simple instructions for creating and starting threads
An NSThread object represents a thread

Create and start threads

(1) NSThread *thread = [[NSThread alloc] initWithTarget:self selector:@selector(run) object:nil];

[thread start];

//As soon as the thread starts, it will execute the self run method in the thread

Main thread related usage

• (NSThread *)mainThread; / / get the main thread

• (BOOL)isMainThread; / / whether it is the main thread

• (BOOL)isMainThread; / / whether it is the main thread

Other uses

Get current thread

NSThread *current = [NSThread currentThread];

Scheduling priority of thread: the value range of scheduling priority is 0.0 ~ 1.0, and the default is 0.5. The larger the value is, the higher the priority is

• (double)threadPriority;

• (BOOL)setThreadPriority:(double)p;

Set the name of the thread

• (void)setName:(NSString *)n;

• (NSString *)name;

Other ways to create threads

(2) Automatically start the thread [NSThread detachNewThreadSelector:@selector(run) toTarget:self withObject:nil];

(3) Implicitly create and start the thread [self performSelectorInBackground:@selector(run) withObject:nil];

Advantages and disadvantages of the above two ways to create threads

Advantages: simple and fast

Disadvantage: unable to set the thread in more detail

2, Code example

1. Create in an old way

//
//  YYViewController.m
//
//
//  Created by apple on 14-6-23.
//  Copyright (c) 2014 itcase. All rights reserved
//


#import "YYViewController.h"
#import <pthread.h>


@interface YYViewController ()
- (IBAction)btnClick;
@end


@implementation YYViewController


- (void)viewDidLoad
{
    [super viewDidLoad];
}


//Button click event
- (IBAction)btnClick {
    //1. Get the current thread
    NSThread *current=[NSThread currentThread];
    //Main thread
    NSLog(@"btnClick----%@",current);   

    //2. Use for loop to perform some time-consuming operations
   pthread_t thread;
    pthread_create(&thread, NULL, run, NULL);
}


//c language function
void *run(void *data)
{
    //Get the current thread, which is a newly created thread
    NSThread *current=[NSThread currentThread];


    for (int i=0; i<10000; i++) {
        NSLog(@"btnClick---%d---%@",i,current);
    }
    return NULL;
}

//Multiple threads. When clicking the button to execute the method call, the main thread is not blocked

@end

Effect:

Print results:

2. Use NSThread to create thread

//
//  YYViewController.m
//
//
//  Created by apple on 14-6-23.
//  Copyright (c) 2014 itcase. All rights reserved
//

#import "YYViewController.h"
#import <pthread.h>


@interface YYViewController ()
- (IBAction)btnClick;
@end


@implementation YYViewController 

- (void)viewDidLoad
{
    [super viewDidLoad];
}


//Button click event
- (IBAction)btnClick {
    //1. Get the current thread
    NSThread *current=[NSThread currentThread];
    //Main thread
    NSLog(@"btnClick----%@",current);

    //Another way to get the main thread
   NSThread *main=[NSThread mainThread];
    NSLog(@"Main thread-------%@",main);

    //2. Perform some time-consuming operations
    [self creatNSThread];
//    [self creatNSThread2];
//    [self creatNSThread3];
}


/**
 * NSThread Create thread mode 1
 * 1> Create initialization thread first
 * 2> start Open thread
 */
-(void)creatNSThread
{
    NSThread  *thread=[[NSThread alloc]initWithTarget:self selector:@selector(run:) object:@"thread A"];
    //Set a name for the thread
    thread.name=@"thread A";
     //Open thread
    [thread start];


    NSThread  *thread2=[[NSThread alloc]initWithTarget:self selector:@selector(run:) object:@"thread B"];
    //Set a name for the thread
    thread2.name=@"thread B";
   //Open thread
    [thread2 start];
}


/**
 * NSThread Create thread mode 2
*Start the thread directly (automatically) after creation
 */

-(void)creatNSThread2
{
//    NSThread *thread=[NSThread detachNewThreadSelector:@selector(run:) toTarget:self withObject: @ "start directly (automatically) after thread creation"];

    [NSThread detachNewThreadSelector:@selector(run:) toTarget:self withObject:@"After thread creation, directly(automatic)start-up"];
}


/**
 * NSThread Create thread mode 3
 * Implicitly create threads and start them directly (automatically)
 */

-(void)creatNSThread3
{
    //Execute in background thread = = = execute in child thread
    [self performSelectorInBackground:@selector(run:) withObject:@"Implicit creation"];
}



-(void)run:(NSString *)str
{
   //Get current thread
    NSThread *current=[NSThread currentThread];
    //Printout
    for (int i=0; i<10; i++) {
       NSLog(@"run---%@---%@",current,str);
    }
}
@end

Call thread 1, and the print result is:

Call thread 2

Call thread 3