多线程创建 方法二：NSOperation & NSOperationQueue

加载的图片显示如下：

工程结构：

//
//  RootViewController.m
//  operationPrac1
//
//  Created by zm on 14-11-26.
//  Copyright (c) 2014年 practice. All rights reserved.
//

/**
 *  第二种创建线程的方式   block 实现
 *
 *  NSOperation & NSOperationQueue
 */

#define TAG_OFFSET 101

#import "RootViewController.h"
#import "MyOperation.h"

@interface RootViewController ()

@end

@implementation RootViewController

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
    if (self) {

    }
    return self;
}


- (void)viewDidLoad
{
    [super viewDidLoad];

    NSArray *urlArray = [NSArray arrayWithObjects:
                         @"http://p0.meituan.net/mmc/b5415ecd02850feaac07b5f1a95c040b46622.jpg",
                         @"http://p0.meituan.net/mmc/b5415ecd02850feaac07b5f1a95c040b46622.jpg",
                         @"http://p0.meituan.net/mmc/b5415ecd02850feaac07b5f1a95c040b46622.jpg", nil];
   
    for (int i = 0; i < urlArray.count; i++) {
        float x = i*100;
        UIImageView *imageView = [[UIImageView alloc] initWithFrame:CGRectMake(x, 100, 80, 80)];
        imageView.tag = 101+i;
        [self.view addSubview:imageView];
    }
    
    // 创建线程池
    NSOperationQueue *queue = [[NSOperationQueue alloc] init];
    for (int i = 0; i < urlArray.count; i++) {
        
        MyOperation *operation = [[MyOperation alloc]initWithStrUrl:[urlArray objectAtIndex:i] andCompletionCallback:^(MyOperation *operation, NSData *data) {
            int tag = operation.tag;
            UIImage *image = [UIImage imageWithData:data];
            UIImageView *imageView = (UIImageView *)[self.view viewWithTag:tag];
            imageView.image = image;
        }];
        
        operation.tag = TAG_OFFSET + i;
        [queue addOperation:operation];//将线程加入到线程池中
    }
    
}

- (void)didReceiveMemoryWarning
{
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

/*
#pragma mark - Navigation

// In a storyboard-based application, you will often want to do a little preparation before navigation
- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
    // Get the new view controller using [segue destinationViewController].
    // Pass the selected object to the new view controller.
}
*/

@end
           

//
//  MyOperation.h
//  operationPrac1
//
//  Created by zm on 14-11-26.
//  Copyright (c) 2014年 practice. All rights reserved.
//

#import <Foundation/Foundation.h>
@class MyOperation;

typedef void(^CompletionCallback)(MyOperation *operation,NSData *data);

@interface MyOperation : NSOperation

-(id)initWithStrUrl:(NSString *)strUrl andCompletionCallback:(CompletionCallback)callback;

@property (nonatomic,assign) int tag;

@end
           

//
//  MyOperation.m
//  operationPrac1
//
//  Created by zm on 14-11-26.
//  Copyright (c) 2014年 practice. All rights reserved.
//

#import "MyOperation.h"

@interface MyOperation ()<NSURLConnectionDataDelegate>
{
    NSString *_strUrl;
    CompletionCallback _completionCallback;
    NSMutableData *_data;
    BOOL _isFinishDownload;
}

@end

@implementation MyOperation

-(id)initWithStrUrl:(NSString *)strUrl andCompletionCallback:(CompletionCallback)callback
{
    if (self = [super init]) {
        _strUrl = strUrl;
        _completionCallback = [callback copy];
        _data = [NSMutableData data];
        _isFinishDownload = NO;
    }
    return self;
}

-(void)main
{
    //线程开始
    NSLog(@"operation run");
    
    NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString:_strUrl]];
    
    [NSURLConnection connectionWithRequest:request delegate:self];
    
    while(!_isFinishDownload) {
        [[NSRunLoop currentRunLoop] runMode:NSDefaultRunLoopMode beforeDate:[NSDate distantFuture]];
    }
    
    //线程死亡
    NSLog(@"operation complete");
}


#pragma mark - NSURLConnectionDataDelegate

-(void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
{
    _data.length = 0;
}

-(void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
    [_data appendData:data];
}

-(void)connectionDidFinishLoading:(NSURLConnection *)connection
{
    if (_completionCallback) {
        dispatch_async(dispatch_get_main_queue(), ^{
            _completionCallback(self,_data);
        });
    }
}

-(void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error
{
    NSLog(@"error:%@",error);
}


@end