「リファクタリング 第2版」Swiftでコーディング その5

11頁 第1章 play変数の削除 「問い合わせによる一時変数の置き換え(p.185)」

Swift版 main.swift

データ生成、結果表示付き。

import Foundation

makeData()

func playFor(aPerformance:Performance, plays:Dictionary<String, Play>) -> Play {
    return plays[aPerformance.playID]!
}

func statement(invoice:Invoice, plays:Dictionary<String, Play>) -> String {
    var volumeCredits = 0
    var totalAmount = 0
    var result = "Statement for \(invoice.customer)\n"
    let format = NumberFormatter()
    format.numberStyle = .currency
    format.locale = Locale(identifier: "en_US")

    for perf in invoice.performances {
        let play = playFor(aPerformance: perf, plays: plays)
        let thisAcmount = amountFor(aPerformance: perf, play: play)

        volumeCredits += max(perf.audience - 30, 0)
        if "comedy" == play.type {
            volumeCredits += Int(perf.audience / 5)
        }
        result += "  \(play.name): " + format.string(from: NSNumber(value: thisAcmount / 100))! + " (\(perf.audience) seats)\n"
        totalAmount += thisAcmount
    }
    result += "Amount owed is " + format.string(from: NSNumber(value: totalAmount / 100))! + "\n"
    result += "You earned \(volumeCredits) credits\n"
    return result
}

func amountFor(aPerformance:Performance, play:Play) -> Int {
    var result = 0

    switch play.type {
    case "tragedy":
        result = 40000
        if aPerformance.audience > 30 {
            result += 1000 * (aPerformance.audience - 30)
        }
    case "comedy":
        result = 30000
        if aPerformance.audience > 20 {
            result += 10000 + 500 * (aPerformance.audience - 20)
        }
        result += 300 * aPerformance.audience
    default:
        print("error")
    }
    return result
}
 
let result = statement(invoice: invoices[0], plays: plays)
print(result)