Accessing a non raw type enumerations case values?

Question

So I have an enumeration defined as the following:

enum CardPosition {
    case top(CGFloat) 
    case middle(CGFloat)
    case bottom(CGFloat) 
}

I have a variable of type CardPosition that is defined as:

@State private var position: CardPosition = CardPosition.bottom(UIScreen.main.bounds.height - 100)

How do I access the value of the CardPosition? In this case, I'm trying to access the UIScreen.main.bounds.height - 100 value from the enumeration. I tried accessing it with

self.position.rawValue 

but unfortunately this doesn't work. Anyone know how I can access the CGFloat value of position?

Answer 1

You need to use a switch here:

switch position {
case .top(let f):
    // use f
case .middle(let f):
    // use f
case .bottom(let f):
    // use f
}

If you want it as an expression , you can do something like:

// you can assign the below to a variable or whatever
// let value =
{ () -> CGFloat in
    switch position {
    case .top(let f):
        return f
    case .middle(let f):
        return f
    case .bottom(let f):
        return f
    }
}()

However, I think the best solution is to redesign your types. It seems like there will always be a CGFloat associated with every case of your enum. Why not use a struct composing a simple enum and a CGFloat ?

enum RelativeCardPosition {
    case top
    case middle
    case bottom
}

struct CardPosition {
    let relativeCardPosition: RelativeCardPosition
    let offset: CGFloat
    
    static func top(_ offset: CGFloat) -> CardPosition {
        CardPosition(relativeCardPosition: .top, offset: offset)
    }
    
    static func middle(_ offset: CGFloat) -> CardPosition {
        CardPosition(relativeCardPosition: .middle, offset: offset)
    }
    
    static func bottom(_ offset: CGFloat) -> CardPosition {
        CardPosition(relativeCardPosition: .bottom, offset: offset)
    }
}

Then you can easily access the number via position.offset .

Answer 2

You can create a Computed Property position inside the enum CardPosition and return the associated value with each case , ie

enum CardPosition {
    case top(CGFloat)
    case middle(CGFloat)
    case bottom(CGFloat)
    
    var position: CGFloat {
        switch self {
        case .top(let pos), .middle(let pos), .bottom(let pos):
            return pos
        }
    }
}

Answer 3

To get the associated value for your .bottom variable you use if let case syntax

var position: CardPosition = CardPosition.bottom(UIScreen.main.bounds.height - 100.0)

if case let CardPosition.bottom(positionValue) = position {
    print(positionValue)
}

This will give you only a value for .bottom and not for any of the other enum cases.