Ndtyjky

I would like to know if its possible to have multiple Equatable functions in one class. My current problem is from this example:

class Ingredient: Equatable {



static func == (lhs: Ingredient, rhs: Ingredient) -> Bool {

    return lhs.ingredientId == rhs.ingredientId && lhs.price == rhs.price

}



//    static func == (lhs: Ingredient, rhs: Ingredient) -> Bool {

//        return lhs.ingredientId == rhs.ingredientId && lhs.price == rhs.price && lhs.quantity == rhs.quantity

//    }

}

As you can see I would like to have commented equality function but it doesn't work this way because I already have one. I need both functions working. Is there any optimal solution for this?

No, you can not.

From the math definition of the function:

A function is a process or a relation that associates each element x of a set X, the domain of the function, to a single element y of another set Y (possibly the same set), the codomain of the function.

In general, by defining more than one function with the same name which takes arguments of the same types you create ambiguity which leads to unpredictable results. So this behaviour will generate compile time error.

You can't have multiple definitions of the ==() function (the function that gives you conformance to the equatable protocol) but you can write a complex implementation of your ==() function that uses more complex logic to decide how to compare two objects. You could even add a class variable to your class and have your ==() function use that variable in deciding how to compare values, although that seems like bad design.