Hey guys I am trying to implement the twitter for posting the comments about my music application.For that I use OAuth authentication twitter but it give me error please help out I didn't know anything in this. it show's me this error "'TWITPIC_API_KEY' undeclared (first use in this function)"
if i need some key in this than where to find this key .How to implement this key . Guys I realllly didn't know anything .please help me .
Thanks in advance .
You need to create and generate an API key with Twitter and Twitpic for your application. You can do that at: http://dev.twitter.com/apps (twitter) and http://dev.twitpic.com/apps/new (twitpic)
Once you've created your application on the twitter and twitpic sites, you'll be provided with the keys you need (referred to as consumer key and consumer secret on twitter iirc).
Then, and this is hard to help you with completely as you've not stated which ObjC api you're using or provided code, update or define TWITPIC_API_KEY with your API key.
Implementing oAuth or xAuth to post tweets to twitter may be quite tricky. But to help you out with your problem we need more information on the libraries you are using to implement OAuth.
Your "TWITPIC_API_KEY" error looks like you're using a library not quite suitable for your purpose: I assume you don't want to post your comments as pictures to Twitpic ;-) So, if you want to connect your music app with twitter to post tweets there should be no need for a TWITPIC_API_KEY. You would only need a Twitter-API-Key as dannywartnaby suggested.
Here's a list of OAuth / XAuth / Twitter libraries which you may use for implementing the feature in your application: http://dev.twitter.com/pages/oauth_libraries#objectivec
MGTwitterEngine is quite popular ... but the choice depends on your functionality & licensing needs.