Method

Here's a link to the Swift documentation on Methods and the self property.

actually, I already read about that and I couldn't understand that.I s it like to say what stored in the value = value?

Each new instance of an object you create (ie "instantiate) through the init-method... needs to have it's own versions of the stored properties that come along with the class they belong to..... for example if you create a class of Car that has a stored property such as ... var color: String .....than each new instance of the Car class must have a particular color property of type String...... so that you might reference.... myNewCar.color ...and get back a String value.... Therefore "self" with in a class init method refers to the new instance that will be created at instantiation....

class Car {

var color: String  // stored property "color" of type String must be included with each new Car instance....
init(color: String) {
    self.color = color  //  each new version of Car (self) will be assigned the color provided at instantiation.....
}

}

let myNewCar = Car(color: "Red") //example of Car instantiation......(instantiation == creating a new "instance" of the class)

if (myNewCar.color == "Red") { print("I understand.......'self' refers to each new instance!") }