UIViewController isEditing - 属性观察器不起作用

Question

I was trying to implement property observers on my custom UIViewController but I noticed it was not working with the isEditing property.

Do you guys have an idea why?

class MasterViewController: UIViewController {

    // MARK: - Properties

    override var isEditing: Bool {
        didSet {
            print("VC is editing")
        }
    }
}

Answer 1

According to the documentation for isEditing

Use the setEditing(_:animated:) method as an action method to animate the transition of this state if the view is already displayed.

And from setEditing(_:animated:)

Subclasses that use an edit-done button must override this method to change their view to an editable state if isEditing is true and a non-editable state if it is false. This method should invoke super's implementation before updating its view.

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TL;DR

You'll want to override setEditing(_:animated:) instead.

Answer 2

It's for those who can't find any example how setEditing works.

SWIFT 5:

override func setEditing(_ editing: Bool, animated: Bool) {
        if yourTableView.isEditing == true {
            yourTableView.isEditing = false //change back
            
            
        } else {
            yourTableView.isEditing = true // activate editing
            editButtonItem.isSelected = true // select edit button
        }
    }