新建繼承NSObject類Downloader
Downloader.h程式碼

#import <Foundation/Foundation.h>
#import <UIKit/UIKit.h>



//@class Downloader;

typedef void(^Success)(NSMutableData *data,NSString *name);
typedef void(^Failure)(NSError *error);


@protocol ProGress <NSObject>

-(void)postPro:(CGFloat)pro;//代理實現進度傳遞
 


@end

@interface Downloader : NSObject <NSURLConnectionDataDelegate>
{
    long long _length;//檔案大小
    NSMutableData *_datas;
    long long _currenLenght;//當前下載的檔案大小

}

@property (nonatomic, assign) long long length;
@property (nonatomic, strong) NSMutableData *datas;
@property (nonatomic, copy) Success success;
@property
 
 (nonatomic, copy) Failure failure;

@property (nonatomic, strong) NSString *strURL;
@property (nonatomic,strong)NSString *fileName;

@property (nonatomic,assign)id<ProGress>proDelegate;

- (void)asynchronousDownload:(NSString *)url failure:(Failure)failure;


@end

Downloader.m程式碼

//
//  Downloader.m
 

//  QNNSEC
//
//  Created by chenp on 16/5/25.
//  Copyright © 2016年 chenp. All rights reserved.
//

#import "Downloader.h"

@implementation Downloader


- (void)asynchronousDownload:(NSString *)strURL
{
    _currenLenght=0;
    self.strURL = strURL;
    NSURL *url = [NSURL URLWithString:[strURL stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding]];

    NSURLRequest *request = [NSURLRequest requestWithURL:url cachePolicy:NSURLRequestReloadIgnoringCacheData timeoutInterval:10];

    [NSURLConnection connectionWithRequest:request delegate:self];
}


- (void)asynchronousDownload:(NSString *)url failure:(Failure)failure
{
    self.failure = failure;

    [self asynchronousDownload:url];
}

- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
{
    _length = response.expectedContentLength;
    _datas = [NSMutableData dataWithCapacity:_length];
    self.fileName= [response suggestedFilename];
}

- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
    _currenLenght+=data.length;
    [self.datas appendData:data];
    if (self.proDelegate && [self.proDelegate conformsToProtocol:@protocol(ProGress)]) {
        [self.proDelegate postPro:(CGFloat)_currenLenght/(CGFloat)_length];
    }
}

- (void)connectionDidFinishLoading:(NSURLConnection *)connection
{
    NSLog(@"--->> Downloader 下載完成");
    self.success(self.datas,self.fileName);
}

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


@end