Sometimes we want to design our own UI for "Sign In With Facebook" button instead of the original button that comes with FacebookSDK.
Swift:
    let loginButton = FBSDKLoginButton()
    loginButton.delegate = self
    // Your Custom Permissions Array
    loginButton.readPermissions =
    [
                             "public_profile",
                             "email",
                             "user_about_me",
                             "user_photos"
    ]
    // Hiding the button
    loginButton.hidden = true
    self.view.addSubview(loginButton)
    // Simulating a tap for the actual Facebook SDK button
    loginButton.sendActionsForControlEvents(UIControlEvents.TouchUpInside)
Objective-C:
FBSDKLoginButton *FBButton = [FBSDKLoginButton new];
// Your Custom Permissions Array
FBButton.readPermissions = @[@"public_profile",
                             @"email",
                             @"user_about_me",
                             @"user_photos"
                             ];
FBButton.loginBehavior = FBSDKLoginBehaviorNative;
[FBButton setDelegate:self];
[FBButton setHidden:true];
[loginButton addSubview:FBButton];
[FBButton sendActionsForControlEvents:UIControlEventTouchUpInside];
You're done.