Swift - Repeating Code Using Loops(Repetition Based on User Input, switch/case, lowercaseString, input function)

The Swift Programming Language
Apple Inc.

開発環境

• OS X Mavericks - Apple(OS)
• Xcode 6.0 Beta 6
• Swift (プログラミング言語)

Practical Programming: An Introduction to Computer Science Using Python 3 (Pragmatic Programmers) (Paul Gries (著)、Jennifer Campbell (著)、Jason Montojo (著)、Lynn Beighley (編集)、Pragmatic Bookshelf)のChapter 9(Repeating Code Using Loops)、9.10(Exercises) 6.をSwiftで考えてみる。

9.10(Exercises) 6.

コード(Xcode)

main.swift

//
//  main.swift
//  sample6
//
//  Created by kamimura on 9/7/14.
//  Copyright (c) 2014 kamimura. All rights reserved.
//

import Foundation

var text:String = ""

while text.lowercaseString != "quit" {
    text = input()
    switch text {
    case let s where s.lowercaseString == "quit":
        println("…exiting program")
    case "H2O":
        println("Water")
    case "NH3":
        println("Ammonia")
    case "CH4":
        println("Methane")
    default:
        println("Unknown compound")
    }
}

stdio.swift

//
//  stdio.swift
//  stdio
//
//  Created by kamimura on 8/21/14.
//  Copyright (c) 2014 kamimura. All rights reserved.
//

import Foundation

// 標準入力(STDIN)から読み込む
func input(msg:String = "") -> String {
    print(msg)
    var in_fh = NSFileHandle.fileHandleWithStandardInput()
    var data = in_fh.availableData
    var s = NSString(data: data, encoding: NSUTF8StringEncoding)
    s = s.substringToIndex(s.length - 1)
    return s
}

func read(path:String) -> String? {
    return String.stringWithContentsOfFile(path)
}

func print(s:String, path:String, end:String = "\n") {
    (s + end).writeToFile(path, atomically: true, encoding: NSUTF8StringEncoding, error: nil)
}

func error(msg:String) {
    let stderr = NSFileHandle.fileHandleWithStandardError()
    stderr.writeData((msg + "\n").dataUsingEncoding(NSUTF8StringEncoding)!)
    exit(1)
}

// コマンドライン引数
let argv:[String] = NSProcessInfo.processInfo().arguments.map({(x:AnyObject) -> String in x as String})

入出力結果(Console Output)

$ ./sample6 
quit
…exiting program
$ ./sample6 
Quit
…exiting program
$ ./sample6 
QUIT
…exiting program
$