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iOS多线程之自定义NSOperation

iOS自定义NSOperation

1.步骤：

重写- (void)main方法，在里面实现想执行的操作（例如图片下载等耗时操作）

2.注意点

1》自己创建自动释放池

2》通过- (BOOL)isCancelled方法检测操作是否被取消，对取消做出响应

3.下面我们简单以图片下载为例自定义一个NSOpeartion ，LLDownloadOperation

LLDownloadOperation.h

@class LLDownloadOperation; @protocol DownloadOperationDelegate <NSObject> @optional -(void)downloadOperation:(LLDownloadOperation *)operation didFineshDownloadImage:(UIImage *)image; @end //自定义要继承子NSOperation @interface LLDownloadOperation : NSOperation ///下载的链接 @property (nonatomic,copy) NSString *urlStr; ///代理 @property (nonatomic,assign) id <DownloadOperationDelegate> delegate; @end

LLDownloadOperation.m

#import "LLDownloadOperation.h" @implementation LLDownloadOperation -(void)main{  @autoreleasepool { //自己创建自动释放池   if (self.isCancelled) return; //通过- (BOOL)isCancelled方法检测操作是否被取消   NSURL *url=[NSURL URLWithString:self.urlStr];   NSData *data=[NSData dataWithContentsOfURL:url];   if (self.isCancelled) return; //通过- (BOOL)isCancelled方法检测操作是否被取消   if(data!=nil){    UIImage *image=[UIImage imageWithData:data];      //通知代理    if ([self.delegate respondsToSelector:@selector(downloadOperation:didFineshDownloadImage: withIndexPath:)]) {     dispatch_async(dispatch_get_main_queue(), ^{      [self.delegate downloadOperation:self didFineshDownloadImage:image withIndexPath:self.indexPath];     });    }   }  } } @end

4.使用

LLDownloadOperation *operation=[[LLDownloadOperation alloc] init]; operation.urlStr=url; operation.delegate=self; self.queue.maxConcurrentOperationCount=2; [self.queue addOperation:operation];   //异步下载 -(NSOperationQueue *)queue{  if (!_queue) {   _queue=[[NSOperationQueue alloc] init];  }  return _queue; } #pragma mark - DownloadOperation Delegate -(void)downloadOperation:(LLDownloadOperation *)operation didFineshDownloadImage:(UIImage *)image{    NSLog(@“%@“,image); }

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