自己封装的下载方法

1.MyDownloader.h文件

 1 #import <Foundation/Foundation.h>
 2 
 3 //前置声明
 4 @class MyDownloader;
 5 //协议
 6 @protocol MyDownloaderDelegate <NSObject>
 7 
 8 //下载失败
 9 - (void)downloader:(MyDownloader *)downloder failWithReeor:(NSError *)error;
10 
11 //下载成功,并且下载结束
12 - (void)downloaderFinish:(MyDownloader *)downloader;
13 
14 @end
15 
16 
17 //NSURLConnectionDelegate协议用来处理下载是成功还是失败
18 //NSURLConnectionDataDelegate 用来处理下载成功时的网络返回的数据
19 @interface MyDownloader : NSObject<NSURLConnectionDelegate,NSURLConnectionDataDelegate>
20 //下载的方法
21 -(void)downloadWithUrlString:(NSString *)urlString;
22 
23 //代理属性:
24 //MRC:assign  ARC:weak
25 /*
26         基本类型     代理属性    其它对象
27  MRC    assign      assign    retain
28  ARC    assign      weak      strong
29  */
30 @property (nonatomic,weak)id<MyDownloaderDelegate>delegate;
31 
32 //获取下载回来的数据(_receiveData)
33 //readonly 表示只会自动生成的getter方法
34 @property (nonatomic,strong)NSData *receiveData;
35 //类型
36 @property (nonatomic,assign)NSInteger type;
37 
38 @end

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2.MyDownloader.m文件

 1 #import "MyDownloader.h"
 2 @implementation MyDownloader
 3 {
 4     //下载对象
 5     NSURLConnection *_conn;
 6     //储存下来的数据
 7     NSMutableData *_receiveData;
 8 }
 9 
10 -(instancetype)init
11 {
12     self = [super init];
13     if (self) {
14         //初始化下载数据的对象
15         _receiveData = [NSMutableData data];
16     }
17     return self;
18 }
19 
20 -(void)downloadWithUrlString:(NSString *)urlString
21 {
22     //1.创建NSURL类型的对象
23     NSURL *url = [NSURL URLWithString:urlString];
24     
25     //2.创建NSURLRequest类型的对象
26     NSURLRequest *request = [NSURLRequest requestWithURL:url];
27     
28     //3.创建NSURLConnection类型的对象
29     _conn = [NSURLConnection connectionWithRequest:request delegate:self];
30 }
31 
32 #pragma mark  -  NSURLConnection代理
33 //下载成功
34 //准备接受数据
35 -(void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
36 {
37     [_receiveData setLength:0];
38 }
39 //接受下载回来的数据
40 -(void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
41 {
42     [_receiveData appendData:data];
43 }
44 //下载完成
45 //程序会自动切换到主线程
46 -(void)connectionDidFinishLoading:(NSURLConnection *)connection
47 {
48     if (self.delegate) {
49         [self.delegate downloaderFinish:self];
50     }
51 }
52 //下载失败
53 -(void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error
54 {
55     if (self.delegate) {
56         [self.delegate downloader:self failWithReeor:error];
57     }
58 }
59 
60 @end

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