closure.swift

struct ComputerLab { // Computer Lab contains list of laptops.
    let laptops: [Laptop]
}
// we want to get the list of mac laptops

// Traditional way
var macLaptops: [Laptop] = []
for laptop in computerLab.laptops {
    if laptop.name.contains("Mac") {
        macLaptops.append(laptop)
    }
}

// Swifty way or Functional way
// filter is an higher order function which takes the predicate
// and gives the subset which satisfies the predicate.
let macLaptops = computerLab.laptops.filter { (laptop: Laptop) -> Bool in
    return laptop.name.contains("Mac")
}
// Simplificaton 1: Types can be inferred. So we can remove types
let macLaptops = computerLab.laptops.filter { laptop in
    return laptop.name.contains("Mac")
}

// Simplificaton 2: If there is one line function, return is optional
let macLaptops = computerLab.laptops.filter { laptop in laptop.name.contains("Mac") }

// Simplificaton 3: Shorthand argument names. $0 for first argument.
let macLaptops = computerLab.laptops.filter { $0.name.contains("Mac") }