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iOS

Posted by Alexander Certosimo
Alexander Certosimo
1,774 Points

what is self doing here?

I was wondering is someone could help me understand exactly what self is doing here? thanks for your time

enum Day: Int {
    case Monday = 1, Tuesday, Wednesday, Thursday, Friday, Saturday, Sunday

    func daysTillWeekend()->Int {
        return Day.Saturday.rawValue - self.rawValue
    }
}


var today = Day.Monday
today.daysTillWeekend()

4 Answers

Sam Chaudry
Sam Chaudry
25,519 Points

Self is a keyword used in Swift to refer to an instance of a object. This can be a Class, Enums Structs etc all of which are data structures containing data properties (i.e. weatherConditions:String).

In this case you have an enum called Day of type Int. So when you want to determine the rawValue of this enum you would say self.rawValue. Which is saying give me the rawValue of Enum named Day, or programatically self.rawValue.

Hope this clarifies things

Alexander Certosimo
Alexander Certosimo
1,774 Points

thank you, sam

Would the Enum Day be the instance and its members be the objects?

Sam Chaudry
Sam Chaudry
25,519 Points
Sam Chaudry
Sam Chaudry
25,519 Points

Yeah spot on

Alexander Certosimo
Alexander Certosimo
1,774 Points
Alexander Certosimo
Alexander Certosimo
1,774 Points

Hi Sam,

Thank you. just to clarify a bit more since i have been really trying to grasp the concept of object oriented programming. in the above example, when we assign Day.Monday to the variable total, we are creating an object of type Day, correct? Which we can also say we are creating an instance?

Sam Chaudry
Sam Chaudry
25,519 Points
Sam Chaudry
Sam Chaudry
25,519 Points

Yeah basically you create object and instantiate them when you are using them. A good for you might be this:

https://alfredjava.wordpress.com/2008/07/08/class-vs-object-vs-instance/