ios 自写网络请求实例方法

+ (void)downloadDataWithURLString:(NSString *)urlstring AndSuccess:(void (^)(NSData *))success AndFailed:(void (^)(void))failed

{

dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0),^{

NSURL *lURL = [NSURL URLWithString:urlstring];

NSData *lData = [NSData dataWithContentsOfURL:lURL];

if (lData == nil)

{

dispatch_sync(dispatch_get_main_queue(), ^{

failed();

});

return ;

}

dispatch_sync(dispatch_get_main_queue(), ^{

success(lData);

});

});

}