Swift Pattern Matching, Part 3: Custom pattern matching & syntactic sugar. Shakyo practice.

PatternMatchingPart3.swift

/*
 From http://alisoftware.github.io/swift/pattern-matching/2016/04/24/pattern-matching-3/
 
 Shakyo practice
 
 Pattern Matching, Part 3: Custom pattern matching & syntactic sugar
 */


import XCPlayground
import Foundation
import UIKit


// MARK: - Simply Range Pattern Match

0...100 ~= 15

// MARK: - Use Operator Overloading 1

struct Affine {
    var a: Int
    var b: Int
}

func ~= (leftSide: Affine, rightSide: Int) -> Bool {
    return rightSide % leftSide.a == leftSide.b
}

switch 5 {
case Affine(a: 2, b: 0): print("Even")
case Affine(a: 3, b: 1): print("3x+1")
case Affine(a: 3, b: 2): print("3x+2")
default: print("default")
}

// MARK: - Use Operator Overloading 2

struct Book {
    let title: String
    let author: String
    let publishYear: Int
}

func ~= (leftSide: Range<Int>, rightSide: Book) -> Bool {
    return leftSide ~= rightSide.publishYear
}

let book = Book(title: "Roadside Picnic", author: "Arkady and Boris Strugatsky", publishYear: 1972)
switch book {
    case 1900..<1950: print("1900...<1950")
    case 1950..<2000: print("1950..<2000")
    default: print("default")
}

// MARK: - Use Operator Overloading 3

struct Answer {
    let text: String
    let compareOptions: NSStringCompareOptions = [
        .CaseInsensitiveSearch,       // 大文字小文字区別しない
        .DiacriticInsensitiveSearch,  // 記号を無視
        .WidthInsensitiveSearch       // 半角,全角の幅の違いを無視
    ]
}

func ~= (leftSide: Answer, rightSide: String) -> Bool {
    return leftSide.text.compare(rightSide, options: leftSide.compareOptions, range: nil, locale: nil) == NSComparisonResult.OrderedSame
}

let userAnswer = "Tete a Tete"

switch userAnswer {
case Answer(text: "tête-à-tête"): print("Good answer!")
case Answer(text: "tête à tête"): print("Almost… don't forget dashes!")
default: print("Sorry, wrong answer!")
}

// MARK: -  indexPath and case ….rawValue

let indexPath : NSIndexPath =  NSIndexPath(forRow: 2, inSection: 0)
indexPath.row

enum MenuItem: Int {
    case Home
    case Account
    case Setting
}

switch indexPath.row {
    case MenuItem.Home.rawValue:    print("Home")
    case MenuItem.Account.rawValue: print("Accopunt")
    case MenuItem.Setting.rawValue: print("Setting")
    default: print("default")
}

// ↓ enum from the rawValue first.

switch MenuItem(rawValue: indexPath.row) {
    case .Home?:print("Home")
    case .Account?:print("Account")
    case .Setting?:print("Setting")
    default: print("default")
}

// ↓ one more !!

guard let menuItem = MenuItem(rawValue: indexPath.row) else {
    fatalError("indexPath invalid")
}

switch menuItem {
    case .Home:print("Home")
    case .Account:print("Account")
    case .Setting:print("Setting")
}