使用parse.com登出后台

I am new to creating apps and am trying to make an app that uses parse.com for logging in and out using Xcode 7 and Swift. I have so far made sign up and login screens and a home screen with, so far, only a sign out button. I have an IBAction method called "signOut" that is triggered when the sign out button is pressed. Inside it I have just two lines of code:I am new to creating apps and am trying to make