title: how to set facebook app id in iOS
body: <p>I thought an app need to submit the App ID to facebook server to pass OAuth , getting user's permission , then get the active session to read/post information. </p>
  
  <p>I am looking for something like:</p>
  
  <pre><code>Facebook fb = new Facebook("YOUR_APP_ID");
  </code></pre>
  
  <p>I checked the "Facebook iOS SDK" tutorials and project "HelloFacebookSample" , but did not find any code to set my App ID. How to set my App ID and App Secret? How to make "HelloFacebookSample" to use my App , instead of using the official sample app?
  I am using Xcode. Thanks.</p>