Can't change custom class of UIButton to GIDSignInButton

You should try assign GIDSignInButton not to the Button Object from the Object library but to the the View Object instead

It's work for me.

It will look like this using UIView instead of UIButton.

That's because GIDSignInButton is a subclass of UIView, not UIButton. Add to the storyboard / nib a regular UIView and change it's class to GIDSignInButton instead.

From google doc:

Add a GIDSignInButton to your storyboard, XIB file, or instantiate it programmatically. To add the button to your storyboard or XIB file, add a View and set its custom class to GIDSignInButton.

You can create UIButton and then on its action method you can write this code for signing via google:

    GIDSignIn.sharedInstance().signIn()

It works for me, in this way you can customize UIButton according to your requirement and also perform signin by using google