Property observers willSet and didSet; Property getters and setters

Question

What is the difference between willSet - didSet, and get - set, when working with this inside a property?

From my

Answer 1

get set:

get set are Computed Properties Which do not actually store a value. Instead, they provide a getter and an optional setter to retrieve and set other properties and values indirectly

Additionally you can define Read-Only Computed Properties. A read-only computed property always returns a value, and can be accessed through dot syntax, but cannot be set to a different value

Example get only property-

 var number: Double {
        return .pi*2
    }

willSet didSet:

willSet didSet are Property Observers

Property observers observe and respond to changes in a property’s value. Property observers are called every time a property’s value is set, even if the new value is the same as the property’s current value.

• willSet is called just before the value is stored.
• didSet is called immediately after the new value is stored.

Example -

var score: Int = 0 {
    willSet(newScore) {
        print("willSet  score to \(newScore)")
    }
    didSet {
        print("didSet score to \(oldValue) new score is: \(score)")
    }
}
score = 10
//Output 
//willSet  score to 10
//didSet score to 0 new score is: 10

https://developer.apple.com/library/content/documentation/Swift/Conceptual/Swift_Programming_Language/Properties.html