swift - What is the actual meaning of " ! " prefix in Swift?

Question

I want to know about prefix !. I have created an app, and it has tableView. And I have used setEditing:animated property for editing a tableView, it allows multiple selection. When user start selecting? We need to cancel segue operations. Of course we need to override shouldPerformSegueWithIdentifier method. Here's my code

override func shouldPerformSegueWithIdentifier(identifier: String, sender: AnyObject?) -> Bool {
        return !editing
    }

Firstly I've tried to use return editing. Xcode does not gave me any errors even run time errors. Everything seems to works just fine. But segues are still works. And then I've tried to use with prefix return !editing. Works perfect! What's the actual meaning of this prefix ! ?

Thanks

Answer 1

!运算符是布尔值的逻辑非；即!true变成false，!false变成true。