17.swift How to listen for changes to this property

Import UIKit

class Person: NSObject {

var name: String? {

// can give newvalue a custom name

willset (new) { //The property is about to change and the method that is called when it is not changed

// In this method there is a default system attribute NewValue, which is used to store the new value

Print (name)

Print (new)

}

// can give oldValue a custom name

didset (old) { // property value has changed , the method that will be called

// In this method there is a default system attribute , OldValue, for storing old values

Print (name)

Print (old)

}

}

var age: Int = 0

var height: Double = 0.0

}

Let P: Person = person()

// when assigning , listen for changes to this property

// in OC by overriding the set method

// in Swift , You can add listeners to a property

P. Name = "Why"

P.name = "YZ"

17.swift How to listen for changes to this property