Standard Library Functions

Standard Library Functions.swift

let values = [1,2,3,4,5]

var newArray = [Int]()
for number in values {
    newArray.append(number * 2)
}

let tripledValues = values.map { $0 * 3 }

// Map

extension Array {
    func map<T>(transform: Element -> T) -> [T] {
        var result = [T]()
        
        for x in self {
            result.append(transform(x))
        }
        return result
    }
}

let intergerValues = ["1", "2", "3", "a", "4"].map { Int($0) }

import Foundation

struct Formatter {
    static let formatter = NSDateFormatter()
    
    static func dateFromString(dateString: String) -> NSDate? {
        formatter.dateFormat = "d MMM yyyy"
        return formatter.dateFromString(dateString)
    }
}

let dateStrings = ["10 Oct 1988", "11 Jan 1947", "28 Mar 2002"]

let dates = dateStrings.map { Formatter.dateFromString($0) }

// Flat Map

struct Post {
    var content: String
    var tags: [String]
}

let blog = [
    Post(content: "Hello, world!", tags: ["first", "programming"]),
    Post(content: "Just another short post", tags: ["general"])
]

blog.map { $0.content }

let tags = blog.map { $0.tags }

let flattenedTags = blog.flatMap { $0.tags }

extension Array {
    func flatMap<T>(transform: Element -> [T]) -> [T] {
        var result = [T]()
        
        for x in self {
            result.appendContentsOf(transform(x))
        }
        
        return result
    }
}

// Example 2

import UIKit

struct Account {
    let username: String
    let billingAddress: String?
}


let allUsers = [
    Account(username: "pasanpr", billingAddress: nil),
    Account(username: "benjakuben", billingAddress: "1234 Imaginary Street"),
    Account(username: "instantNadel", billingAddress: "5678 Doesn't Live Here Dr."),
    Account(username: "sketchings", billingAddress: nil),
    Account(username: "paradoxed", billingAddress: "1122 Nope Lane")
]

let validAddresses = allUsers.flatMap { $0.billingAddress }
validAddresses

// Filter

let evenNumbers = (0...100).filter { $0 % 2 == 0 }
evenNumbers

extension Array {
    func filter(includeElement: Element -> Bool) -> [Element] {
        var result = [Element]()
        
        for x in self where includeElement(x) {
            result.append(x)
        }
        
        return result
    }
}

let pUser = allUsers.filter { $0.username.characters.first == "p" }

// Reduce

let scores = [10, 12, 11, 10, 12, 9]

let totalScore = scores.reduce(0, combine: {total, score in total + score })

extension Array {
    func reduce<T>(inital: T, combine: (T, Element) -> T) -> T {
        var result = inital
        
        for x in self {
            result = combine(result, x)
        }
        
        return result
    }
}

let dataSet = (1...100).filter { $0 % 3 == 0 && $0 % 7 == 0 }
let identifier = dataSet.reduce("", combine: {str, num in str + "\(num)"})

identifier