How replace position++ code to make it Swift 3 compatible?

Question

I have following class, which has method getNextToken to iterate array items:

class Parser {
    let tokens: [Token]
    var position = 0

    i         


        

Answer 1

One way is to assign the token to a let constant before incrementing position:

func getNextToken() -> Token? {
    guard position < tokens.count else {
        return nil
    }
    let token = tokens[position]
    position += 1
    return token
}

Another way is to save off the current value of position:

func getNextToken() -> Token? {
    guard position < tokens.count else {
        return nil
    }
    let current = position
    position += 1
    return tokens[current]
}

Or you could undo the increment:

func getNextToken() -> Token? {
    guard position < tokens.count else {
        return nil
    }
    position += 1
    return tokens[position - 1]
}

Answer 2

defer can be used to increment the position variable after the return value has been computed:

func getNextToken() -> Token? {
    guard position < tokens.count else {
        return nil
    }
    defer {
        position += 1
    }
    return tokens[position]
}