When you download the FB SDK you get a sample project. Compile and run it, and you should see a toggle button that allows user to login/logout. You've got the FB official images in that project, and the code behind it is pretty simple:
/**
* Called on a login/logout button click.
*/
- (void)fbButtonClick:(id)sender {
if (fbButton.isLoggedIn) {
[self logout];
} else {
[self login];
}
}
/**
* Show the authorization dialog.
*/
- (void)login {
[_facebook authorize:nil delegate:self];
NSLog(@"Sas");
}
/**
* Invalidate the access token and clear the cookie.
*/
- (void)logout {
[_facebook logout:self];
}
You should also change the button's state in the FBAuth delegate methods (which you've already implemented) by calling a method similar to this one:
- (void)updateFbButtonAccordingToSessionStatus {
//Check if session is valid and update button accordingly
if ([self.facebook isSessionValid] == NO ) {
fbButton.isLoggedIn = NO;
[fbButton updateImage];
}
else {
fbButton.isLoggedIn = YES;
[fbButton updateImage];
}
}
Hope this helps.
