I am having to update my method of posting to Twitter now that OAuth
is going to be compulsory. Here is what has worked out for me: adding
library OAuthCore (http://bitbucket.org/atebits/oauthcore)

then:

        NSString *consumerKey = @"consumer key";             //replacing
values accordingly
        NSString *consumerSecret = @"consumer secret";
        NSString *accessToken = @"access token";
        NSString *accessTokenSecret = @"access secret";
        NSString *method=@"POST";

        NSURL *url = [NSURL URLWithString:@"http://twitter.com/statuses/
update.xml"];   // API call as appropriate

        ASIFormDataRequest *request = [ASIFormDataRequest
requestWithURL:url];

        [request setPostValue:[tweetTextField stringValue] forKey:@"status"];

        [request buildPostBody];
        NSData *body = [request postBody];

        NSString *header = OAuthorizationHeader(url, method, body,
consumerKey, consumerSecret, accessToken, accessTokenSecret);

        [request addRequestHeader:@"Authorization" value:header];

Hope this helps anyone else in this situation. This is working in Mac
OS X 10.5

Any comments on the subject are welcome

thanks.

Paul