Swift - Reading and Writing Files(function(reading backward though a file), read, String extension(split method, reversed), stdio(argv))

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 10(Reading and Writing Files)、10.10(Exercises) 3.をSwiftで考えてみる。

10.10(Exercises) 3.

コード(Xcode)

main.swift

//
//  main.swift
//  sample3
//
//  Created by kamimura on 9/25/14.
//  Copyright (c) 2014 kamimura. All rights reserved.
//

import Foundation

func readBackward(path:String) -> String {
    return read(path)!.reversed
}

println(readBackward(argv[1]))

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
    in_fh.closeFile()
    var s = NSString(data: data, encoding: NSUTF8StringEncoding)
    s = s?.substringToIndex(s!.length - 1)
    return s!
}

func read(path:String) -> String? {
    var fh = NSFileHandle(forReadingAtPath: path)
    let data = fh?.readDataToEndOfFile()
    if fh == nil {
        error("file(\(path)) can't open.")
    }
    fh?.closeFile()
    return NSString(data: data!, encoding: NSUTF8StringEncoding)
}

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})

string.swift

//
//  string.swift
//  string
//
//  Created by kamimura on 8/10/14.
//  Copyright (c) 2014 kamimura. All rights reserved.
//

import Foundation

extension String {
    var swapcaseString:String {
    var result: String = ""
        for ch in self {
            let s = String(ch)
            result += s.uppercaseString == s ? s.lowercaseString : s.uppercaseString
        }
        return result
    }
    var isUpper:Bool { return self.uppercaseString == self }
    var isLower:Bool { return self.lowercaseString == self }
    var length:Int { return (self as NSString).length }
    var strip:String { return self.stringByTrimmingCharactersInSet(NSCharacterSet.whitespaceAndNewlineCharacterSet())}
    var floatValue:Float { return (self as NSString).floatValue }
    var doubleValue:Double { return (self as NSString).doubleValue }
    func count(sub:String) -> Int {
        var result:Int = 0
        var s = self
        let index:String.Index = "a".endIndex
        while s != "" {
            if s.hasPrefix(sub) {
                result += 1
                s = s.substringFromIndex(sub.endIndex)
            } else {
                s = s.substringFromIndex(index)
            }
            
        }
        return result
    }
    func find(sub:String, start:Int = 0, end:Int? = nil) -> Int {
        var s = self as NSString
        var s_temp = s.substringFromIndex(start)
        let end_temp:Int = end != nil ? end! : s.length
        for i in start..<end_temp {
            if (s_temp.hasPrefix(sub)) {
                return i
            }
            s_temp = s.substringFromIndex(i + 1) as NSString
        }
        return -1
    }
    func indexAt(i:Int) -> String {
        if i >= 0 {
            return (self as NSString).substringWithRange(NSRange(location: i, length: 1))
        }
        let new_i = self.length + i
        return (self as NSString).substringWithRange(NSRange(location: new_i, length: 1))
    }
    func replace(old_str:String, new_str:String) -> String {
        return self.stringByReplacingOccurrencesOfString(old_str, withString: new_str)
    }
    func slice(start:Int=0, end:Int?=nil) -> String {
        let s = self as NSString
        var new_end:Int
        if (end != nil) {
            new_end = end!
        } else {
            new_end = s.length
        }
        return  s.substringWithRange(NSRange(location: start, length:new_end - start))
    }
    func split(sep:String = "") -> [String] {
        var result:[String] = []
        if (sep == "") {
            for ch in self {
                result.append(String(ch))
            }
            return result
        }
        var s:String = self
        var len = sep.length
        var temp:String = ""
        while s != "" {
            if s.hasPrefix(sep) {
                if temp != "" {
                    result.append(temp)
                    temp = ""
                }
                s = s.slice(start: len)
            } else {
                temp += s.slice(start: 0, end: 1)
                s = s.slice(start: 1)
            }
        }
        if temp != "" {
            result.append(temp)
        }
        return result
    }
    var reversed:String { return "".join(self.split().reverse()) }
    func repeat(n:Int) -> String {
        var result:String = ""
        for i in 0..<n {
            result += self
        }
        return result
    }
}

func * (left:String, right:Int) -> String{
    return left.repeat(right)
}

func * (left:Int, right:String) -> String{
    return right.repeat(left)
}

入出力結果(Console Output)

$ ./sample3 alkaline_metals.txt 

622 88 muidar
723.731 65 muirab
26.78 83 muitnorts
870.02 02 muiclac
503.42 21 muisengam
210.9 4 muillyreb
$ cat alkaline_metals.txt 
beryllium 4 9.012
magnesium 12 24.305
calcium 20 20.078
strontium 38 87.62
barium 56 137.327
radium 88 226
$