一. NSOperation简介
简单说明
NSOperation的作用：配合使用NSOperation和NSOperationQueue也能实现多线程编程
NSOperation和NSOperationQueue实现多线程的具体步骤：先将需要执行的操作封装到一个
NSOperation对象中然后将
NSOperation对象添加到NSOperationQueue中系统会自动将
NSOPerationQueue中的NSOperation取出来将取出的
NSOperation封装的操作放到一条新线程中执行
2.NSoperation的子类
NSOperation是个抽象类，并不具备封装操作的能力，必须使用它的子类使用
NSOperation子类的方式有三种NSInvocationOperationNSBlockOperation自定义子类继承NSOperation,实现内部相应的方法
二.具体说明
1.NSInvocationOperation子类
创建对象和执行操作：
NSInvocationOperation * operation = [[NSInvocationOperation alloc]initWithTarget:self selector:@selector(testTarget) object:nil];
[operation start];
说明：一旦执行操作，就会调用Target的testTarget方法
代码示例：
//
// ViewController.m
// TestNSOperationQueue
//
// Created by taobaichi on 2017/3/21.
// Copyright © 2017年 MaChao. All rights reserved.
//
#import "ViewController.h"
@interface ViewController ()
@end
@implementation ViewController
- (void)viewDidLoad {
[super viewDidLoad];
NSInvocationOperation * operation = [[NSInvocationOperation alloc]initWithTarget:self selector:@selector(testTarget) object:nil];
[operation start];
}
-(void)testTarget {
NSLog(@"-------test---%@---",[NSThread currentThread]);
}
打印结果：
2017-03-21 11:16:05.385 TestNSOperationQueue[3648:99757] -------test---<NSThread: 0x6080000775c0>{number = 1, name = main}---
注意：操作对象默认在主线程中执行，只有添加到队列中才会开启新的线程，即默认情况下，如果操作没有放到队列中queue中，都是同步执行，只有将
NSOperation放到一个NSOperationQueue中，才会以异步执行
2.NSBlockOperation子类
- 创建对象和添加操作:
NSBlockOperation * operation = [NSBlockOperation blockOperationWithBlock:^{
//......
}];
operation addExecutionBlock:^{
//......
};
-
代码示例：
- 代码1：
//
// ViewController.m
// TestNSOperationQueue
//
// Created by taobaichi on 2017/3/21.
// Copyright © 2017年 MaChao. All rights reserved.
//
#import "ViewController.h"
@interface ViewController ()
@end
@implementation ViewController
- (void)viewDidLoad {
[super viewDidLoad];
NSBlockOperation * operation = [NSBlockOperation blockOperationWithBlock:^{
NSLog(@"NSBlockOperation------%@",[NSThread currentThread]);
}];
[operation start];
}
@end
打印结果：
2017-03-21 11:37:21.540 TestNSOperationQueue[4033:113489] NSBlockOperation------<NSThread: 0x60800006a3c0>{number = 1, name = main}
- 代码2：
//
// ViewController.m
// TestNSOperationQueue
//
// Created by taobaichi on 2017/3/21.
// Copyright © 2017年 MaChao. All rights reserved.
//
#import "ViewController.h"
@interface ViewController ()
@end
@implementation ViewController
- (void)viewDidLoad {
[super viewDidLoad];
NSBlockOperation * operation = [NSBlockOperation blockOperationWithBlock:^{
NSLog(@"NSBlockOperation------%@",[NSThread currentThread]);
}];
[operation addExecutionBlock:^{
NSLog(@"NSBlockOperation1------%@",[NSThread currentThread]);
}];
[operation addExecutionBlock:^{
NSLog(@"NSBlockOperation2------%@",[NSThread currentThread]);
}];
[operation start];
}
@end
打印结果：
2017-03-21 11:39:36.710 TestNSOperationQueue[4085:115570] NSBlockOperation1------<NSThread: 0x608000261240>{number = 4, name = (null)}
2017-03-21 11:39:36.710 TestNSOperationQueue[4085:115571] NSBlockOperation------<NSThread: 0x600000267dc0>{number = 3, name = (null)}
2017-03-21 11:39:36.710 TestNSOperationQueue[4085:115529] NSBlockOperation2------<NSThread: 0x60800007dc00>{number = 1, name = main}
注意：只要NSBlockOperation封装的操作数 > 1,就会异步执行操作
3.NSOperationQueue
NSOperationQueue的作用：NSOperation可以调用start方法来执行，但默认是同步执行的
如果将
NSOperation添加到NSOperationQueue（操作队列）中，系统会自动异步执行NSOperation中的操作
添加操作到NSOperationQueue中，自动执行操作，自动开启线程
NSInvocationOperation * operation1 = [[NSInvocationOperation alloc]initWithTarget:self selector:@selector(testOperation1) object:nil];
NSInvocationOperation * operation2 = [[NSInvocationOperation alloc]initWithTarget:self selector:@selector(testOperation2) object:nil];
NSInvocationOperation * operation3 = [[NSInvocationOperation alloc]initWithTarget:self selector:@selector(testOperation3) object:nil];
//创建NSOperationQueue
NSOperationQueue * queue = [[NSOperationQueue alloc]init];
//把操作添加到队列中
//第一种方式
[queue addOperation:operation1];
[queue addOperation:operation2];
[queue addOperation:operation3];
//第二种方式
[queue addOperationWithBlock:^{
NSLog(@"-------testOperationBlock-----");
}];
代码示例：
//
// ViewController.m
// TestNSOperationQueue
//
// Created by taobaichi on 2017/3/21.
// Copyright © 2017年 MaChao. All rights reserved.
//
#import "ViewController.h"
@interface ViewController ()
@end
@implementation ViewController
- (void)viewDidLoad {
[super viewDidLoad];
//创建NSInvocationOperation对象，封装操作
NSInvocationOperation * operation1 = [[NSInvocationOperation alloc]initWithTarget:self selector:@selector(testOperation1) object:nil];
NSInvocationOperation * operation2 = [[NSInvocationOperation alloc]initWithTarget:self selector:@selector(testOperation2) object:nil];
//创建对象，封装操作
NSBlockOperation * operation3 = [NSBlockOperation blockOperationWithBlock:^{
NSLog(@"-----NSBlockOperation--3--1---- %@",[NSThread currentThread]);
}];
[operation3 addExecutionBlock:^{
NSLog(@"-----NSBlockOperation--3--2---- %@",[NSThread currentThread]);
}];
//创建NSOperationQueue
NSOperationQueue * queue = [[NSOperationQueue alloc]init];
//把操作添加到队列中
[queue addOperation:operation1];
[queue addOperation:operation2];
[queue addOperation:operation3];
}
-(void)testOperation1
{
NSLog(@"-----NSInvocationOperation--1---- %@",[NSThread currentThread]);
}
-(void)testOperation2
{
NSLog(@"-----NSInvocationOperation--2---- %@",[NSThread currentThread]);
}
@end
打印效果：
2017-03-21 13:36:39.594 TestNSOperationQueue[5185:159392] -----NSInvocationOperation--2---- <NSThread: 0x60800007b480>{number = 4, name = (null)}
2017-03-21 13:36:39.594 TestNSOperationQueue[5185:159391] -----NSInvocationOperation--1---- <NSThread: 0x600000269f40>{number = 3, name = (null)}
2017-03-21 13:36:39.594 TestNSOperationQueue[5185:159394] -----NSBlockOperation--3--1---- <NSThread: 0x60000026a0c0>{number = 5, name = (null)}
2017-03-21 13:36:39.594 TestNSOperationQueue[5185:159414] -----NSBlockOperation--3--2---- <NSThread: 0x608000266240>{number = 6, name = (null)}
注意：系统自动将
NSOperationQueue中的NSOperation对象取出，将其封装的操作放到一条新的线程中执行，上面的代码示例一共有四个任务，operation1和operation2分别有一个任务，operation3有2个任务。一共四个任务，开启了四条线程，通过任务执行的时间全部是2017-03-21 13:36:39.594可以看出，这些任务是并行执行的
提示：队列的取出是有顺序的，与打印结果并不矛盾。这就好比，选手A,B，C虽然起跑的顺序是先A,后B，然后C，但是到达终点的顺序却不一定是A,B在前，C在后。
下面使用for循环打印，可以更明显的看出任务是并行执行的
代码示例：
//
// ViewController.m
// TestNSOperationQueue
//
// Created by taobaichi on 2017/3/21.
// Copyright © 2017年 MaChao. All rights reserved.
//
#import "ViewController.h"
@interface ViewController ()
@end
@implementation ViewController
- (void)viewDidLoad {
[super viewDidLoad];
//创建NSInvocationOperation对象，封装操作
NSInvocationOperation * operation1 = [[NSInvocationOperation alloc]initWithTarget:self selector:@selector(testOperation1) object:nil];
NSInvocationOperation * operation2 = [[NSInvocationOperation alloc]initWithTarget:self selector:@selector(testOperation2) object:nil];
//创建对象，封装操作
NSBlockOperation * operation3 = [NSBlockOperation blockOperationWithBlock:^{
for (int i = 0; i < 5; i++) {
NSLog(@"-----NSBlockOperation----3--1---- %@",[NSThread currentThread]);
}
}];
[operation3 addExecutionBlock:^{
for (int i = 0; i < 5; i++) {
NSLog(@"-----NSBlockOperation----3--2---- %@",[NSThread currentThread]);
}
}];
//创建NSOperationQueue
NSOperationQueue * queue = [[NSOperationQueue alloc]init];
//把操作添加到队列中
[queue addOperation:operation1];
[queue addOperation:operation2];
[queue addOperation:operation3];
}
-(void)testOperation1
{
for (int i = 0; i < 5; i++) {
NSLog(@"-----NSInvocationOperation--1---- %@",[NSThread currentThread]);
}
}
-(void)testOperation2
{
for (int i = 0; i < 5; i++) {
NSLog(@"-----NSInvocationOperation--2---- %@",[NSThread currentThread]);
}
}
@end
打印结果：
2017-03-21 13:51:44.091 TestNSOperationQueue[5519:170579] -----NSBlockOperation----3--1---- <NSThread: 0x608000074f80>{number = 5, name = (null)}
2017-03-21 13:51:44.091 TestNSOperationQueue[5519:170582] -----NSInvocationOperation--2---- <NSThread: 0x608000075140>{number = 4, name = (null)}
2017-03-21 13:51:44.090 TestNSOperationQueue[5519:170580] -----NSInvocationOperation--1---- <NSThread: 0x60800006f200>{number = 3, name = (null)}
2017-03-21 13:51:44.091 TestNSOperationQueue[5519:170644] -----NSBlockOperation----3--2---- <NSThread: 0x6080000752c0>{number = 6, name = (null)}
2017-03-21 13:51:44.094 TestNSOperationQueue[5519:170579] -----NSBlockOperation----3--1---- <NSThread: 0x608000074f80>{number = 5, name = (null)}
2017-03-21 13:51:44.096 TestNSOperationQueue[5519:170580] -----NSInvocationOperation--1---- <NSThread: 0x60800006f200>{number = 3, name = (null)}
2017-03-21 13:51:44.096 TestNSOperationQueue[5519:170582] -----NSInvocationOperation--2---- <NSThread: 0x608000075140>{number = 4, name = (null)}
2017-03-21 13:51:44.099 TestNSOperationQueue[5519:170644] -----NSBlockOperation----3--2---- <NSThread: 0x6080000752c0>{number = 6, name = (null)}
2017-03-21 13:51:44.100 TestNSOperationQueue[5519:170579] -----NSBlockOperation----3--1---- <NSThread: 0x608000074f80>{number = 5, name = (null)}
2017-03-21 13:51:44.101 TestNSOperationQueue[5519:170580] -----NSInvocationOperation--1---- <NSThread: 0x60800006f200>{number = 3, name = (null)}
2017-03-21 13:51:44.103 TestNSOperationQueue[5519:170582] -----NSInvocationOperation--2---- <NSThread: 0x608000075140>{number = 4, name = (null)}
2017-03-21 13:51:44.103 TestNSOperationQueue[5519:170644] -----NSBlockOperation----3--2---- <NSThread: 0x6080000752c0>{number = 6, name = (null)}
2017-03-21 13:51:44.105 TestNSOperationQueue[5519:170579] -----NSBlockOperation----3--1---- <NSThread: 0x608000074f80>{number = 5, name = (null)}
2017-03-21 13:51:44.105 TestNSOperationQueue[5519:170580] -----NSInvocationOperation--1---- <NSThread: 0x60800006f200>{number = 3, name = (null)}
2017-03-21 13:51:44.106 TestNSOperationQueue[5519:170582] -----NSInvocationOperation--2---- <NSThread: 0x608000075140>{number = 4, name = (null)}
2017-03-21 13:51:44.108 TestNSOperationQueue[5519:170644] -----NSBlockOperation----3--2---- <NSThread: 0x6080000752c0>{number = 6, name = (null)}
2017-03-21 13:51:44.112 TestNSOperationQueue[5519:170579] -----NSBlockOperation----3--1---- <NSThread: 0x608000074f80>{number = 5, name = (null)}
2017-03-21 13:51:44.113 TestNSOperationQueue[5519:170580] -----NSInvocationOperation--1---- <NSThread: 0x60800006f200>{number = 3, name = (null)}
2017-03-21 13:51:44.117 TestNSOperationQueue[5519:170582] -----NSInvocationOperation--2---- <NSThread: 0x608000075140>{number = 4, name = (null)}
2017-03-21 13:51:44.119 TestNSOperationQueue[5519:170644] -----NSBlockOperation----3--2---- <NSThread: 0x6080000752c0>{number = 6, name = (null)}
实战： 实现一个下载图片的例子
//
// ViewController.m
// TestNSOperationQueue
//
// Created by taobaichi on 2017/3/21.
// Copyright © 2017年 MaChao. All rights reserved.
//
#import "ViewController.h"
#define kURL @"http://avatar.csdn.net/2/C/D/1_totogo2010.jpg"
@interface ViewController ()
@property (nonatomic, strong) UIImageView * imagView;
@end
@implementation ViewController
- (void)viewDidLoad {
[super viewDidLoad];
self.imagView = [[UIImageView alloc]initWithFrame:CGRectMake(self.view.frame.size.width/2 - 50, self.view.frame.size.height/2 - 50, 100, 100)];
self.imagView.backgroundColor = [UIColor lightGrayColor];
[self.view addSubview:self.imagView];
//创建一个后台线程，后台线程执行downloadImage方法
NSInvocationOperation * operation = [[NSInvocationOperation alloc]initWithTarget:self selector:@selector(downloadImage:) object:kURL];
//创建NSOperationQueue
NSOperationQueue * queue = [[NSOperationQueue alloc]init];
//把创建的后台线程放到NSOperationQueue中
[queue addOperation:operation];
}
-(void)downloadImage:(NSString *)url
{
NSLog(@"url: %@",url);
NSURL * nsUrl = [NSURL URLWithString:url];
NSData * data = [[NSData alloc]initWithContentsOfURL:nsUrl];
UIImage * image = [[UIImage alloc]initWithData:data];
//下载完成后执行主线程updateUI方法
[self performSelectorOnMainThread:@selector(updateUI:) withObject:image waitUntilDone:YES];
}
-(void)updateUI:(UIImage *)image
{
self.imagView.image = image;
}
@end
代码注释：
- viewDidLoad方法里可以看到我们用NSInvocationOperation建了一个后台线程，并且放到NSOperationQueue中。后台线程执行downloadImage方法。
- downloadImage 方法处理下载图片的逻辑。下载完成后用performSelectorOnMainThread执行主线程updateUI方法。
- updateUI 并把下载的图片显示到图片控件中。
运行后可以看到下载图片显示在界面上
Simulator Screen Shot 2017年3月21日 14.29.48.png
