I have two arrays like this:
var arrayA = [\"Mike\", \"James\", \"Stacey\", \"Steve\"]
var arrayB = [\"Steve\", \"Gemma\", \"James\", \"Lucy\"]
matt and freytag's solutions are the ONLY ones that account for duplicates and should be receiving more +1s than the other answers.
Here is an updated version of matt's answer for Swift 3.0:
var arrayA = ["Mike", "James", "Stacey", "Steve"]
var arrayB = ["Steve", "Gemma", "James", "Lucy"]
for word in arrayB {
if let ix = arrayA.index(of: word) {
arrayA.remove(at: ix)
}
}