httpDNS IOS如何接入接口

NSString *originalUrl = @"http://gw.alicdn.com";

    NSURL* url = [NSURL URLWithString:originalUrl];
    NSMutableURLRequest* request = [[NSMutableURLRequest alloc] initWithURL:url];
    // 同步接口获取IP
    NSString* ip = [httpdns getIpByHost:url.host];
    if (ip) {
        // 通过HTTPDNS获取IP成功，进行URL替换和HOST头设置
        NSLog(@"Get IP(%@) for host(%@) from HTTPDNS Successfully!", ip, url.host);
        NSRange hostFirstRange = [originalUrl rangeOfString: url.host];
        if (NSNotFound != hostFirstRange.location) {
            NSString* newUrl = [originalUrl stringByReplacingCharactersInRange:hostFirstRange withString:ip];
            request = [[NSMutableURLRequest alloc] initWithURL:[NSURL URLWithString:newUrl]];
            [request setValue:url.host forHTTPHeaderField:@"host"];
        }
    }