To answer my own question.
myapp:// does not meet specification. You must add a path. something like myapp://oauth , or just use myapp: (without a slash)
you must also implement - (BOOL)application:(UIApplication *)application handleOpenURL:(NSURL *)url method in your application. there you will get your myapp://oauth?oauth_token=xxx&oauth_verifier=yyy to start the access token.
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