Swift枚举作为数组的索引

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.

Answer 1

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!