How to find index of list item in Swift?

Question

I am trying to find an item index by searching a list. Does anybody know how to do that?

I see there is list.StartIndex and <

Answer 1

You can filter an array with a closure:

var myList = [1, 2, 3, 4]
var filtered = myList.filter { $0 == 3 }  // <= returns [3]

And you can count an array:

filtered.count // <= returns 1

So you can determine if an array includes your element by combining these:

myList.filter { $0 == 3 }.count > 0  // <= returns true if the array includes 3

If you want to find the position, I don't see fancy way, but you can certainly do it like this:

var found: Int?  // <= will hold the index if it was found, or else will be nil
for i in (0..x.count) {
    if x[i] == 3 {
        found = i
    }
}

EDIT

While we're at it, for a fun exercise let's extend Array to have a find method:

extension Array {
    func find(includedElement: T -> Bool) -> Int? {
        for (idx, element) in enumerate(self) {
            if includedElement(element) {
                return idx
            }
        }
        return nil
    }
}

Now we can do this:

myList.find { $0 == 3 }
// returns the index position of 3 or nil if not found