Using NSPredicate to Filter an Array

let heroes = ["tracer", "bastion", "reaper", "junkrat", "roadhog"]

let template = NSPredicate(format: "self BEGINSWITH $letter")

let beginsWithRVariables = ["letter": "r"]
let beginsWithR = template.predicateWithSubstitutionVariables(beginsWithRVariables)

let beginsWithRHeroes = heroes.filter { beginsWithR.evaluateWithObject($0) }
// ["reaper", "roadhog"]

let beginsWithTVariables = ["letter": "t"]
let beginsWithT = template.predicateWithSubstitutionVariables(beginsWithTVariables)

let beginsWithTHeroes = heroes.filter { beginsWithT.evaluateWithObject($0) }
// ["tracer"]