iOS 下载文件

 - (void)downloadFileFromPath:(NSString *)path withParams:(NSDictionary *)params andFileName:(NSString *)fileName progress:(KSUploadProgress)progress finished:(KSFinishedBlock)finished failed:(KSFailedBlock)failed

{

    NSURLSessionConfiguration *configuration = [NSURLSessionConfiguration defaultSessionConfiguration];

    AFURLSessionManager *manager = [[AFURLSessionManager alloc] initWithSessionConfiguration:configuration];

    NSURLRequest *request = [[AFHTTPRequestSerializer serializer] requestWithMethod:@"POST" URLString:path parameters:params error:nil];
    
    NSURLSessionDownloadTask *downloadTask = [manager downloadTaskWithRequest:request progress:^(NSProgress *downloadProgress){
        if (progress) {
            progress(downloadProgress);
        }
    }destination:^NSURL *(NSURL *targetPath, NSURLResponse *response) {
        NSURL *documentsDirectoryURL = [[NSFileManager defaultManager] URLForDirectory:NSDocumentDirectory inDomain:NSUserDomainMask appropriateForURL:nil create:NO error:nil];
        if (fileName && fileName.length > 0) {
            return [documentsDirectoryURL URLByAppendingPathComponent:fileName];
        }else{
            return [documentsDirectoryURL URLByAppendingPathComponent:[response suggestedFilename]];
        }
    } completionHandler:^(NSURLResponse *response, NSURL *filePath, NSError *error) {
        if (!error) {
            NSHTTPURLResponse *httpResponse = (NSHTTPURLResponse *)response;
            if (httpResponse.statusCode == 200) {
               // 下载成功返回保存本地的地址
                finished(@{@"filePath":filePath});
                } else {
                    failed([NSString stringWithFormat:@"%@",@(httpResponse.statusCode)]);
                }
        } else {
            failed(error.description);
        }
        
    }];
    [downloadTask resume];
}