Swift

Collections

Higher Order Functions

Given the following

struct Person {
    let firstname: String
    let lastname: String
    let age: Int
}

let personArray = [
    Person(firstname: "Rynaard", lastname: "Burger", age: 36),
    Person(firstname: "Foo", lastname: "Bar", age: 24)
]

map

Apply transformations to items in the collection.

let uppercasedFirstnames = personArray.map { $0.firstname.uppercased() }

compactMap (replaced flatMap in Swift 4.1)

Transform each item in the collection and remove any items which are nil.

let mixedArray = ["1", "2", "3", "Dog"]
let numbersOnly = mixedArray.compactMap { Int($0) }

filter

Filters out items in a collection.

let filteredArray = personArray.filter { $0.firstname == "Foo" }

reduce

Reduces the collection down to a single result.

let combinedAge = personArray.reduce(0) { (result, next) -> Int in
    return result + next.age
}

sort

Sort by optional date.

let arraySortedByDate = messages.sorted {
    let date1 = $0.createdAt ?? Date.distantPast
    let date2 = $1.createdAt ?? Date.distantPast

    return date1 > date2
}

Dictionaries

Get all the keys

let keys = dict.map{$0.key}

Get all the values

let values = dict.map{$0.value}