自定义一个下载类

来源：互联网发布：斑马标签打印机软件编辑：程序博客网时间：2024/05/01 04:56

1.新建一个cocoa类，取名Downloader，基类为NSObject。

2.新建类代码

////  Downloader.h//  OnlineMusic#import <Foundation/Foundation.h>// 定义一个BLOCKtypedef void(^DownloadBlock) (NSData *resultsData);@interface Downloader : NSObject// 单例操作:获取类的一个对象+ (instancetype) sharedInstance;// 提供下载的方法-(void)downloadWithURL: (NSURL*)url complete: (DownloadBlock)block;@end

////  Downloader.m//  OnlineMusic//#import "Downloader.h"@interface Downloader ()@property (nonatomic, copy) DownloadBlock block;@end// 全局静态单例对象static Downloader *instance = nil;@implementation Downloader+ (instancetype) sharedInstance {    if (instance == nil)    {        instance = [[[self class] alloc] init];    }    return instance;}-(void) downloadWithURL:(NSURL *)url complete:(DownloadBlock)block{    // 保存block    self.block = block;        dispatch_queue_t queue = dispatch_queue_create(nil, DISPATCH_QUEUE_CONCURRENT);    dispatch_async( queue, ^{        // 执行下载任务        // 创建一个request        NSURLRequest *request = [NSURLRequest requestWithURL:url cachePolicy:NSURLRequestReloadIgnoringCacheData timeoutInterval:60];                // 获取数据        NSData *data = [NSURLConnection sendSynchronousRequest:request returningResponse:nil error:nil];                // 将数据返回给调用者        dispatch_sync(dispatch_get_main_queue(), ^{            self.block(data);        });    });}@end

3.在主视图ViewController类的初始化函数中增加调度

- (void)viewDidLoad {    [super viewDidLoad];    // Do any additional setup after loading the view, typically from a nib.        // other codes                               // 下载数据.注意:如果提供的网址链接不正确，代码运行可能异常    NSURL *url = [NSURL URLWithString:@"http://douban.fm/j/mine/playlist?channel=3"];    [[Downloader sharedInstance] downloadWithURL:url complete:^(NSData* resultData) {        NSDictionary *dic = [NSJSONSerialization JSONObjectWithData:resultData options:NSJSONReadingMutableContainers error:nil];        NSLog(@"%@", dic);    }];}

4.执行后，输出：

2015-09-25 22:24:06.471 OnlineMusic[1432:55597] {    "is_show_quick_start" = 0;    r = 0;    song =     (                {            aid = 1428537;            album = "/subject/1428537/";            albumtitle = "Greatest Hits, Vo...";            "alert_msg" = "";            artist = "Alan Jackson";            "file_ext" = mp3;            kbps = 128;            length = 269;            like = 0;            picture = "http://img4.douban.com/lpic/s1442437.jpg";            sha256 = 97ed83a589d4c952683b5f65ed347af8fd6543c11286e4b74eb0272888f23af6;            sid = 277;            singers =             (                                {                    id = 2900;                    "is_site_artist" = 0;                    name = "Alan Jackson";                    "related_site_id" = 0;                }            );            ssid = c231;            status = 0;            subtype = "";            title = "Little Man";            url = "http://mr7.doubanio.com/170a0467f3d8d87b2f21ace34986559d/0/fm/song/p277_128k.mp3";            ver = 0;        }    );}

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