How to re-request for certain access tokens in Facebook API for iOS
<p>Using the following line of code, I've requested the user to accept the permissions. </p>

<pre><code>loginButton.readPermissions =
                @[@"public_profile", @"email", @"user_friends"];
</code></pre>

<p>In the simulator, I've granted access only for public-profile and email.
Later I wanted to grant an access token for user-friends but the dialog for granting permission no longer appears.
It instead says that "You have already authorized this app" and shows up a Cancel and Ok button.</p>

<p>please help me out! Thanks in advance!:)</p>