google reader api with objective-c-获取令牌时出现问题

我可以成功地获得我的谷歌阅读器帐户的sid(sessionid)。为了获得feed并在Google阅读器内执行其他操作,您必须获得授权令牌。我做这个有困难。有人能发光吗?

//Create a cookie to append to the GET request
NSDictionary *cookieDictionary = [NSDictionary dictionaryWithObjectsAndKeys:@"SID",@"NSHTTPCookieName",self.sessionID,@"NSHTTPCookieValue",@".google.com",@"NSHTTPCookieDomain",@"/",@"NSHTTPCookiePath",nil];
NSHTTPCookie *authCookie = [NSHTTPCookie cookieWithProperties:cookieDictionary];

//The URL to obtain the Token from
NSURL *tokenURL = [NSURL URLWithString:@"http://www.google.com/reader/api/0/token"];
NSMutableURLRequest *tokenRequest = [NSMutableURLRequest requestWithURL:tokenURL];

//Not sure if this is right: add cookie to array, extract the headers from the cookie inside the array...?
[tokenRequest setAllHTTPHeaderFields:[NSHTTPCookie requestHeaderFieldsWithCookies:[NSArray arrayWithObjects:authCookie,nil]]];

//This gives me an Error 403 Forbidden in the didReceiveResponse of the delegate
[NSURLConnection connectionWithRequest:tokenRequest delegate:self];

我从谷歌那里得到了403个被禁止的错误。我可能做得不对。我根据nshtpcookie的文档设置字典值。