Iterate over collection two at a time in Swift

Question

Say I have an array [1, 2, 3, 4, 5]. How can I iterate two at a time?

Iteration 1: (1, 2)
Iteration 2: (3, 4)
Iteration 3: (5, nil)

Answer 1

One approach would be to encapsulate the array in a class. The return values for getting pairs of items would be optionals to protect against out-of-range calls.

Example:

class Pairs {

    let source = [1, 2, 3, 4, 5]  // Or set with init()
    var offset = 0

    func nextpair() -> (Int?, Int?) {
        var first: Int? = nil
        var second: Int? = nil
        if offset < source.count {
            first = source[offset]
            offset++
        }
        if offset < source.count {
            second = source[offset]
            offset++
        }
        return (first, second)
    }

}