</pre><pre name="code" class="objc">//// ImageDownloader.h// LessonImageDownLoader-01#import <Foundation/Foundation.h>// 声明一个协议@protocol ImageDownlodaerDelegate <NSObject>// 成功返回数据- (void)imageDownSucceedWithData:(NSData *)data;// 失败返回错误信息- (void)imageDownFailedWithData:(NSError *)error;@end@interface ImageDownloader : NSObject// 声明一个代理属性@property (nonatomic, assign) id<ImageDownlodaerDelegate> delegate;// 声明初始化方法- (instancetype)initWithImageUl:(NSString *)imageUrl delegate:(id<ImageDownlodaerDelegate>)delegate;- (void)start;- (void)cancel;@end#import "ImageDownloader.h"// 没有延展 添加一个@interface ImageDownloader () <NSURLConnectionDelegate, NSURLConnectionDataDelegate>// 声明一个可变data 接收数据@property (nonatomic, retain) NSMutableData *data;//声明连接 便于访问@property (nonatomic, retain) NSURLConnection *connection;@end@implementation ImageDownloader-(void)dealloc{// 终止请求最好写在控制器里// [_connection cancel];[_data release];[_connection release];[super dealloc];}- (instancetype)initWithImageUl:(NSString *)imageUrl delegate:(id<ImageDownlodaerDelegate>)delegate{self = [super init];if (self) {// 设置代理_delegate = delegate;//进行图片请求// 创建URL对象NSURL *url = [NSURL URLWithString:imageUrl];// 创建一个请求NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url cachePolicy:(NSURLRequestUseProtocolCachePolicy) timeoutInterval:30];// 创建一个连接 用代理方法self.connection = [NSURLConnection connectionWithRequest:request delegate:self];// 开启连接// 最好是用这个类的对象去控制开始或者终止 增加灵活性// [self.connection start];}return self;}#pragma mark — 代理方法 —(void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response{// 初始化dataself.data = [NSMutableData data];}-(void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data{[self.data appendData:data];}-(void)connectionDidFinishLoading:(NSURLConnection *)connection{// 加载完成 使用代理 把data传给控制器(因为imageView在控制器创建的)// 外面设置代理了 并且实现了协议中的方法 才让代理去if (_delegate != nil && [_delegate respondsToSelector:@selector(imageDownSucceedWithData:)]) {[_delegate imageDownSucceedWithData:self.data];}}-(void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error{if (_delegate != nil && [_delegate respondsToSelector:@selector(imageDownFailedWithData:)]) {[_delegate imageDownFailedWithData:error];}}-(void)start{[self.connection start];}-(void)cancel{[self.connection cancel];}@end
版权声明：本文为博主原创文章，未经博主允许不得转载。
，有多远，走多远，把足迹连成生命线。
