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

var variable1 : Int = 0 { //It's a store property
    didSet {
        print (variable1)
    }
    willSet(newValue) {
    ..
    }
}

var variable2: Int { //It's a Computed Proprties
    get {
        return variable2
    }
    set (newValue){
    }
}

For detail info of Store property and computed property
So when you are trying to assign the value into variable at that assigning time come the concept of 'didSet' & 'willSet'. As @Maxim says

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

Example of 'willSet' & 'didSet' :

class Number {
   var variable1 : Int = 0 {
        didSet{
            print("didSet called")
        }
        willSet(newValue){
            print("willSet called")
        }

    }
}
print("we are going to add 3")
Number().variable1 = 3
print("we added 3")

//o/p:
we are going to add 3
willSet called
didSet called
we added 3

And generally when two property are dependent at that time 'get' & 'set' used. (It's also used in protocol this is different concept.)

Example of 'get' & 'set':

class EquilateralTriangle{
    var sideLength: Double = 0.0
    init(sideLength: Double){
        self.sideLength = sideLength
    }
    var perimeter: Double {
        get {
            return 3.0 * sideLength
        }
        set {
            sideLength = newValue / 3.0
        }
    }

}

var triangle = EquilateralTriangle(sideLength: 3.0)
print(triangle.perimeter) //o/p: 9.0
triangle.perimeter = 12.0
print(triangle.sideLength) //o/p: 4.0