CODEWITHSUNDEEP
swift
Fred Faust
Fred Faust

Reputation: 6790

Find instance of class from class method

I am trying to create a class method which optionally returns an (already instantiated) instance of the class.

I'm thinking of something like writing the memory address of the instantiated class to a user default key and then trying to return the object at that address but I'm not sure if that's a correct approach or how to do that.

class MyClass {

    let myProperty: String

    required init(myProperty: String) {
        self.myProperty = myProperty
    }

    class func currentClass() -> MyClass? {
        return nil
    }
}

let aNewClass = MyClass(myProperty: "Hi")

// Should return the aNewClass instance:
MyClass.currentClass()

Upvotes: 2

Views: 88

Answers (1)

luk2302
luk2302

Reputation: 57114

You need to create a static property which you assign the already created member to:

class MyClass {
    let myProperty: String
    private static var instance : MyClass?

    required init(myProperty: String) {

        self.myProperty = myProperty

        if MyClass.instance == nil {
            MyClass.instance = self
        }
    }

    class func currentClass() -> MyClass? {
        return MyClass.instance
    }
}

let aNewClass = MyClass(myProperty: "Hi")

This is somewhat similar to the singleton pattern, you can always retrieve the same object back from the class. You could alternatively remove the if around the assignment causing the Class to always return the latest instance if that better suits your need.

Upvotes: 3

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