多线程-NSOperation

#import "ViewController.h"

@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    
    //NSOperation 基于GCD的封装，是一个面向对象的类
    //NSOperation它是一个抽象父类  不会直接使用它 而是使用它的子类
    
    //NSInvocationOperation 是NSOperation的子类 它是以函数作为任务
    NSInvocationOperation *invo = [[NSInvocationOperation alloc]initWithTarget:self selector:@selector(operationRun) object:nil];
    
    //NSBlockOperation 是NSOperation的子类  它是block作为任务
    NSBlockOperation *block = [NSBlockOperation blockOperationWithBlock:^{
        NSLog(@"NSBlockOperation 任务执行了");
    }];
    
    //NSOperationQueue 任务队列
    NSOperationQueue *queue = [[NSOperationQueue alloc]init];
    
    //最大并发数
//    queue.maxConcurrentOperationCount = 2;
    
    //如果最大并发数设置成1 当前队列里的线程就变成了串行的 按照顺序依次执行
//    queue.maxConcurrentOperationCount = 1;
//    
//    //将任务添加到队列里
//    [queue addOperation:invo];
//    [queue addOperation:block];
    
    //线程的依赖关系  前面的任务依赖后面的任务  后面的任务执行完 才执行前面的任务
    [invo addDependency:block];
    //可以添加多个依赖关系
    
    //把任务添加到队列里
    [queue addOperation:invo];
    [queue addOperation:block];
    
    //如果有必要 可以取消线程
//    [block cancel];
    
    //把队列里的任务全部取消
//    [queue cancelAllOperations];
    
    //拿到当前队列
    [NSOperationQueue currentQueue];
    
    //拿到主线程队列
    [NSOperationQueue mainQueue];
}

- (void)operationRun{
    
    NSLog(@"NSInvocationOperation 任务执行了");
}
@end

多线程-NSOperation

#import "ViewController.h"
#import "MyOperation.h"

@interface ViewController ()

@property (nonatomic,strong) MyOperation *operation;

@property (nonatomic,strong) NSOperationQueue *queue;

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    
    self.operation = [MyOperation operationOpenUrl:@"http://onepiece.local/SH/3.jpg"];
    
    self.queue = [[NSOperationQueue alloc]init];
    
    //把自定制的任务 添加到队列里
    [self.queue addOperation:self.operation];
    
    //队列的任务数量  当operationCount为0的时候 说明该队列里的线程全部执行完毕
//    self.queue.operationCount
    //观察者KVO 实时监测operationCount的值
    [self.queue addObserver:self forKeyPath:@"operationCount" options:NSKeyValueObservingOptionNew context:nil];
}

- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary<NSString *,id> *)change context:(void *)context{
    //当operationCount的值为0的时候 让主线程显示数据
    if ([change[@"new"] integerValue] == 0) {
        [self performSelectorOnMainThread:@selector(showImage) withObject:self waitUntilDone:NO];
    }
}

- (void)showImage{
    UIImageView *imageView = [[UIImageView alloc]initWithFrame:self.view.bounds];
    
    imageView.image = self.operation.image;
    
    [self.view addSubview:imageView];
}


@end

#import <Foundation/Foundation.h>
#import <UIKit/UIKit.h>

@interface MyOperation : NSOperation

@property (nonatomic,copy) NSString *urlStr;

@property (nonatomic,strong) UIImage *image;


+(instancetype)operationOpenUrl:(NSString *)url;




@end

#import "MyOperation.h"

@implementation MyOperation

//自定义Operation需要重写main函数 main函数线程的入口
- (void)main{
    //把耗时的操作写在这里
    NSData *data = [NSData dataWithContentsOfURL:[NSURL URLWithString:self.urlStr]];
    //下载的图片
    self.image = [UIImage imageWithData:data];
}

+(instancetype)operationOpenUrl:(NSString *)url{
    
    MyOperation *operation = [[MyOperation alloc]init];
    operation.urlStr = url;
    
    return operation;
}




@end