写在前面：以前都没有遇到过调用webservice接口的请求，这次遇到了记录一下。首先感谢原作者并附上原文http://www.cocoachina.com/bbs/read.php?tid-456019.html
如若着急解决手上问题可直接往下看。

这里利用最新的第三方网络请求框架AFN3.0

//常规的get请求
- (void)getUsersOfDept:(NSString *)deptId completeHandler:(UsersCompleteHandler)handler{
    NSString *urlStr = [NSString stringWithFormat:[self joinURL:GETUSERSOFDEPTURL], deptId];
    
    [[AFHTTPSessionManager manager] GET:urlStr parameters:nil progress:nil success:^(NSURLSessionDataTask * _Nonnull task, id  _Nullable responseObject) {
        
        NSNumber *statusNumber = [responseObject objectForKey:@"Status"] ;
        if (statusNumber == nil || [statusNumber integerValue] !=0) {
            NSLog(@"load users of dept failed with result %@", responseObject);
            handler(nil, nil);
        } else {
            NSArray *users = [responseObject objectForKey:@"Users"];
            handler(users, nil);
        }
        
    } failure:^(NSURLSessionDataTask * _Nullable task, NSError * _Nonnull error) {
        
        NSLog(@"get users of dept %@", error.localizedDescription);
        handler(nil, error);
        
    }];
    
}

// 利用AFN manager请求webservice接口
+ (void)sendRequestWithURL:(NSString *)url xmlDocument:(DDXMLDocument *)doc
                   success:(void (^)(NSURLSessionDataTask * _Nonnull operation, id  _Nonnull responseObject)) successHandler
                   failure:(void (^)(NSURLSessionDataTask * _Nonnull operation, NSError * _Nonnull error)) failureHandler{
    
    AFHTTPSessionManager *manager = [AFHTTPSessionManager manager];
    manager.responseSerializer = [AFXMLParserResponseSerializer serializer];
    manager.responseSerializer = [AFHTTPResponseSerializer serializer];
    
//    [manager.requestSerializer setValue:@"text/xml;charset=utf-8" forHTTPHeaderField:@"Content-Type"];
    
    // 设置HTTPBody
    [manager.requestSerializer setQueryStringSerializationWithBlock:^NSString *(NSURLRequest *request, NSDictionary *parameters, NSError *__autoreleasing *error) {
        return doc.XMLString;
    }];
    
    [manager POST:url parameters:doc.XMLString progress:nil success:successHandler failure:failureHandler];
    
}