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

@Maxim's answer is for the 1st part of your question.

As for when to use get and set: when you want a computed property. This:

var x: Int

creates a stored property, which is automatically backed up by a variable (not directly accessible though). Setting a value to that property is translated in setting the value in the property, and similarly for getting.

Instead:

var y = {
    get { return x + 5 }
    set { x = newValue - 5}
}

will create a computed property, which is not backed up by a variable - instead you have to provide the implementation of the getter and/or setter, usually reading and writing values from another property and more generally as a result of a computation (hence the computed property name)

Suggested reading: Properties

Note: your code:

var variable2: Int {
    get{
        return variable2
    }
    set (newValue){
    }
}

is wrong because in the get you are trying to return itself, which means calling get recursively. And in fact the compiler will warn you with a message like Attempting to access 'variable2' within its own getter.