网络请求

#import <Foundation/Foundation.h>

//定义下载中的block
typedef void(^ProcessBlock)(NSURLResponse *response,NSData *data,NSError *error);
//定义下载完成的block
typedef void(^CompletionBlock)(NSURLResponse *response,NSData *data,NSError *error);

//接受网络连接协议
@interface CustomConnection : NSURLConnection<NSURLConnectionDataDelegate>

+ (CustomConnection *)sendAsyRequest:(NSURLRequest *)request andProcessBlock:(ProcessBlock)processblock andCompletionBlock:(CompletionBlock)completionblock;

@end

　　

#import "CustomConnection.h"

@interface CustomConnection ()

@property (nonatomic,strong)NSError *error;

@property (nonatomic,strong)NSURLResponse *response;
@property (nonatomic,strong)NSMutableData *data;

@property (nonatomic,strong)CompletionBlock completionBlock;//在这里使用的是strong.引用计数加1（有内存管理）
@property (nonatomic,strong)ProcessBlock processBlock;

@end


@implementation CustomConnection

+ (CustomConnection *)sendAsyRequest:(NSURLRequest *)request andProcessBlock:(ProcessBlock)processblock andCompletionBlock:(CompletionBlock)completionblock
{
    CustomConnection * connection  = [[CustomConnection alloc]initWithRequest:request delegate:nil];
    connection.completionBlock = completionblock;
    connection.processBlock = processblock;
    
    [connection start];
    
    return connection;
}

- (id)initWithRequest:(NSURLRequest *)request delegate:(id)delegate
{
    //指定当前的网络连接工具类的代理对象是自己
    self = [super initWithRequest:request delegate:self];
    if (self) {
        ;
    }
    return self;
}
//收到网络连接响应的时候调用的方法
- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
{
    self.response = response;
    self.data = [[NSMutableData alloc]init];
}
////收到网络链接发送信息时...
- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
    [self.data appendData:data];
    self.processBlock (self.response,self.data,self.error);
}
//收到网络链接结束信息时...
- (void)connectionDidFinishLoading:(NSURLConnection *)connection
{
    self.completionBlock (self.response,self.data,self.error);
}

- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error
{
    self.error = error;
}

@end

　　在使用的时候,

 NSURL *url = [NSURL URLWithString:@"http://www.taopic.com/uploads/allimg/110329/23-11032ZK01593.jpg"];
    NSURLRequest *request = [NSURLRequest requestWithURL:url];
    
    [CustomConnection sendAsyRequest:request andProcessBlock:^(NSURLResponse *response, NSData *data, NSError *error) {
        UIImageView *imageV = [[UIImageView alloc]initWithImage:[UIImage imageWithData:data]];
        imageV.frame = self.view.bounds;
        [self.view addSubview:imageV];
       NSLog(@"下载中") ;
    } andCompletionBlock:^(NSURLResponse *response, NSData *data, NSError *error) {
        NSLog(@"下载完成") ;
        
    }];