Removing objects from an array based on another array

Question

I have two arrays like this:

var arrayA = [\"Mike\", \"James\", \"Stacey\", \"Steve\"]
var arrayB = [\"Steve\", \"Gemma\", \"James\", \"Lucy\"]

Answer 1

The easiest way is by using the new Set container (added in Swift 1.2 / Xcode 6.3):

var setA = Set(arrayA)
var setB = Set(arrayB)

// Return a set with all values contained in both A and B
let intersection = setA.intersect(setB) 

// Return a set with all values in A which are not contained in B
let diff = setA.subtract(setB)

If you want to reassign the resulting set to arrayA, simply create a new instance using the copy constructor and assign it to arrayA:

arrayA = Array(intersection)

The downside is that you have to create 2 new data sets. Note that intersect doesn't mutate the instance it is invoked in, it just returns a new set.

There are similar methods to add, subtract, etc., you can take a look at them