Facebook SSO authorize in safari but not facebook app in my iphone

I am following the guide exactly开发者_如何学运维 to integrate with Facebook. A weird issue that i run into is that, if I,

1. uninstall the facebook app in iphone

2. OR change the facebook.m implementaion to disable facebook app like [self authorizeWithFBAppAuth:NO safariAuth:YES];

The authorize method works well in safari and get back the auth token in the url

However, if I am not doing the above 2, it will switch to facebook app, and after it says 'loading...' for a second, it gets back to me an url saying user denied. (fbxxxxxxxxxxxxx://authorize#error_reason=user%5Fdenied&error=access%5Fdenied&error_description=The%2Buser%2Bdenied%2Byour%2Brequest%2E%3F%5F)

Why it behaves so differently in the native app and browser? Is it a bug in FB iPhone app? I am using the same app and same user to test.

---

double check your iOS Bundle ID in facebook app setting, it has to be exact same as what you define in app.