Swift enums as index to an array

Question

How can I do a simple index into an array using enums in Swift?

I am a C programmer trying to understand Swift. This is perplexing.

var  arr: [String] = ["2.16", "4.3", "0.101"]

enum Ptr: Int {
    case first = 0
    case second = 1
    case third = 2    
}

var ix = Int(Ptr.first)
print (ix)
let e = Double (arr[ix])

`

I would expect that Ptr.first would yield a 0 integer which I could as an index into array arr.

enum Ptr: Int { case first, second, third } let arr = ["2.16", "4.3", "0.101"] let ix: Ptr = .first print (ix) let e = Double(arr[ix.rawValue]) — Leo Dabus
– Leo Dabus, Commented Jul 6, 2019 at 23:46
Thank you. Coming from decades of C programming, Swift is quite counterintuitive. — bbabbitt
– bbabbitt, Commented Jul 7, 2019 at 18:33

Filip Sakel · Accepted Answer · 2019-08-09 19:39:26Z

2

Why it doesn't work is because all cases in your enum (first, second, third) are essentially of type Ptr (the type of your enum). So in order to get 0 you need to access the case's rawValue property which is an Int:

var ix = Ptr.first.rawValue //accessing the case's rawValue property
print (ix)
let e = Double (arr[ix])

Hope that helps!

answered Aug 9, 2019 at 19:39

Filip Sakel

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2 Comments

bbabbitt Over a year ago

Thanks. Why couldn't Apple just stick to C?

Filip Sakel Over a year ago

Well, swift is a really powerful language. I think you will really like it if you get familiar with the language.

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