Ios ASIHTTPRequest基本身份验证失败

我正在使用以下代码：

NSString *params = [NSString stringWithFormat:@"{\"username\": \"%@\", \"password\": \"%@\", \"client_id\": \"%@\", \"client_secret\": \"%@\"}",
                    mFieldUsername.text, mFieldPassword.text, [NTDefaults clientId], [NTDefaults clientSecret]];
NSLog(@"Params:\n%@", params);

NSURL *url = [NSURL URLWithString:[[NTDefaults baseEndpointUrl] stringByAppendingString:@"/api/token.json"]];
ASIHTTPRequest *request = [ASIFormDataRequest requestWithURL:url];
[request addRequestHeader:@"Content-Type" value:@"application/json"];
[request addRequestHeader:@"Content-Length" value:[NSString stringWithFormat:@"%d",params.length]];
[request setAuthenticationScheme:(NSString *) kCFHTTPAuthenticationSchemeBasic];
[request setUsername:@"user"];
[request setPassword:@"pass"];
[request setShouldPresentCredentialsBeforeChallenge:YES];

[request setPostBody:[params dataUsingEncoding:NSUTF8StringEncoding]];

NSLog(@"Post Body: %@", request.postBody);
NSLog(@"Headers: %@", request.requestHeaders);
NSLog(@"URL: %@", url.absoluteString);
[request setDelegate:self];
[request startAsynchronous];

它正在返回：

错误：需要身份验证

有人对此有什么想法吗？成功使用ASIHTTPRequest进行身份验证？

我成功使用：

request.shouldPresentCredentialsBeforeChallenge = YES;
[request addBasicAuthenticationHeaderWithUsername:@"myUser"
                                      andPassword:@"myPass"];

---

我不使用setAuthenticationScheme进行基本身份验证。

谢谢，我认为这与帖子正文有关。我现在用[RequestAddPostValue:mFieldUsername.text-forKey:@“username”设置它；等等。即使如此，你的解决方案也很有帮助……确实有效。谢谢