khawajafarooq

// Application threads
// Background
func BG(_ block: @escaping () -> Void) {
    DispatchQueue.global(qos: .default).async(execute: block)
}

// Main
func UI(_ block: @escaping () -> Void) {
    DispatchQueue.main.async(execute: block)
}

khawajafarooq

var Operations: [String: (Double, Double) -> Double] = [
    "*": { $0 * $1 },
    "+": { $0 + $1 },
    "-": { $1 - $0 },
    "/": { $1 / $0 }
]

let Operators = ["+", "-", "*", "/"]

func postfix(_ expression: String) -> Double {

khawajafarooq

final class Notifiable<T> {
    
    typealias CompletionHandler = ((T) -> ())
    
    private var propertyChanged: CompletionHandler? = nil
    
    var value: T {
        didSet {
            guard let observer = propertyChanged else { return }
            observer(value)

khawajafarooq

import Foundation

let openBrackets: [Character] = ["(", "{", "["]
let closedBrackets: [Character] = [")", "}", "]"]

// overloading ~= empowers your pattern mathing in switch
func ~=<T: Equatable>(pattern: [T], value: T) -> Bool {
    return pattern.contains(value)
}

khawajafarooq

import Foundation

func findTwoMax(_ array: [Int]) -> (Int, Int)? {
    guard array.count > 1 else {
        return nil
    }
    
    var max = Int.min
    var secondMax = Int.min
    

khawajafarooq

import Foundation

enum Suit {
    case hearts
    case spades
    case diamonds
    case clubs
}

extension Suit {

khawajafarooq

import Foundation

enum YearError: Error {
    case empty
    case invalidNumber
    case invalidBirthYear
    case invalidYear
}

extension YearError: CustomStringConvertible {

khawajafarooq

import UIKit

/// Extending error to make it alertable
extension Error {
    
    /// displays alert from source controller
    func alert(with controller: UIViewController) {
        
        let alertController = UIAlertController(title: "Oops ❗️", message: "\(self)", preferredStyle: .alert)
        let okAction = UIAlertAction(title: "OK", style: .default, handler: nil)

khawajafarooq

/* Test Cases
 Input: [1, 2, 3, 4]
 Output: [1, 2, 3, 5]
 
 Input: [1, 2, 9, 9]
 Output: [1, 3, 0, 0]
 
 Input: [9, 9, 9, 9]
 Output: [1, 0, 0, 0]
 

khawajafarooq

import UIKit

public enum AppColor {
    
    case blue
    case gray
    case graySeparator
    
    var rgba: [CGFloat] {
        switch self {