Book | 리펙터링 2판 1장 마무리(1.5~)

1.5 중첩이 난무하는 함수

1.6 계산 단계와 포맷팅 단계 분리하기

1.7 중간 점검: 두 파일(과 두 단계)로 분리됨

• 적용 결과

class PerformanceCalculator {
  constructor(aPerformance, aPlay) {
    this.performance = aPerformance;
    this.play = aPlay;
  }

  get amount() {
    throw new Error("서브클래스에서 처리하도록 설계");
  }

  get volumeCredits() {
    throw new Error("서브클래스에서 처리하도록 설계");
  }
}

class TragedyCalculator extends PerformanceCalculator {
  get amount() {
    let result = 40000;
    if (this.performance.audience > 30)
      result += 1000 * (this.performance.audience - 30);
    return result;
  }
  get volumeCredits() {
    return Math.max(this.performance.audience - 30, 0);
  }
}
class ComedyCalculator extends PerformanceCalculator {
  get amount() {
    let result = 30000;
    if (this.performance.audience > 20)
      result += 1000 + 500 * (this.performance.audience - 20);
    result += 300 * this.performance.audience;

    return result;
  }
  get volumeCredits() {
    return Math.floor(this.performance.audience / 5);
  }
}

export default function createStatementData(invoice, plays) {
  const statementData = {};
  statementData.customer = invoice.customer; // 고객데이터를 중간 데이터로 옮김
  statementData.performances = invoice.performances.map(enrichPerformance);
  statementData.totalAmount = totalAmount(statementData);
  statementData.totalVolumeCredits = totalVolumeCredits(statementData);
  return statementData;

  function enrichPerformance(aPerformance) {
    // 각각 공연별로 이름, 총금액, 총포인트들을 새로할당
    const calculator = createPerformanceCalculator(
      aPerformance,
      playFor(aPerformance)
    );
    const result = Object.assign({}, aPerformance);
    result.play = playFor(result);
    result.amount = calculator.amount;
    result.volumeCredits = calculator.volumeCredits;
    return result; // 얕은복사
  }

  function createPerformanceCalculator(aPerformance, aPlay) {
    switch (aPlay.type) {
      case "tragedy":
        return new TragedyCalculator(aPerformance, aPlay);
      case "comedy":
        return new ComedyCalculator(aPerformance, aPlay);
      default:
        throw new Error(`알 수 없는 장르: ${aPlay.type}`);
    }
  }
  // 타입 (tragedy, comedy)
  function playFor(aPerformance) {
    return plays[aPerformance.playID];
  }

  function totalVolumeCredits(data) {
    return data.performances.reduce((total, p) => total + p.volumeCredits, 0);
  }

  function totalAmount(data) {
    return data.performances.reduce((total, p) => total + p.amount, 0);
  }
}

1.8 다형성을 활용해 계산 코드 재구성하기

1.9 상태 점검: 다형성을 활용하여 데이터 생성하기

• 적용 결과

import INVOICE from "../../invoices.json";
import PLAYS from "../../plays.json";
import createStatementData from "./createStatementData.js";

function statement(invoice, plays) {
  return renderPlainText(createStatementData(invoice, plays));
}

function renderPlainText(data, plays) {
  let result = `청구 내역(고객명: ${data.customer})\n`;
  for (let perf of data.performances) {
    // 청구 내역을 출력한다.
    result += `${perf.play.name}: ${usd(perf.amount)} (${perf.audience}석)\n`;
  }
  result += `총액: ${usd(data.totalAmount)}\n`;
  result += `적립 포인트: ${data.totalVolumeCredits}점\n`;
  return result;
}

function htmlStatement(invoice, plays) {
  return renderHtml(createStatementData(invoice, plays));
}

function renderHtml(data) {
  let result = `<h1>청구 내역(고객명: ${data.customer})</h1>\n`;
  result += `<table>\n`;
  result += `<tr><th>연극</th><th>좌석 수</th><th>금액</th></tr>`;
  for (let perf of data.performances) {
    // 청구 내역을 출력한다.
    result += `<tr><td>${perf.play.name}</td><td>(${perf.audience}석)</td>`;
    result += `<td>${usd(perf.amount)}</td></tr>\n`;
  }
  result += `</table>\n`;
  result += `총액: ${usd(data.totalAmount)}\n`;
  result += `적립 포인트: ${data.totalVolumeCredits}점\n`;
  return result;
}
function usd(aNumber) {
  return new Intl.NumberFormat("en-US", {
    style: "currency",
    currency: "USD",
    minimumFractionDigits: 2
  }).format(aNumber / 100);
}

document.getElementById("app2").innerText = statement(INVOICE[0], PLAYS);
document.getElementById("app").innerHTML = htmlStatement(INVOICE[0], PLAYS);

class PerformanceCalculator {
  constructor(aPerformance, aPlay) {
    this.performance = aPerformance;
    this.play = aPlay;
  }

  get amount() {
    throw new Error("서브클래스에서 처리하도록 설계");
  }

  get volumeCredits() {
    throw new Error("서브클래스에서 처리하도록 설계");
  }
}

class TragedyCalculator extends PerformanceCalculator {
  get amount() {
    let result = 40000;
    if (this.performance.audience > 30)
      result += 1000 * (this.performance.audience - 30);
    return result;
  }
  get volumeCredits() {
    return Math.max(this.performance.audience - 30, 0);
  }
}
class ComedyCalculator extends PerformanceCalculator {
  get amount() {
    let result = 30000;
    if (this.performance.audience > 20)
      result += 1000 + 500 * (this.performance.audience - 20);
    result += 300 * this.performance.audience;

    return result;
  }
  get volumeCredits() {
    return Math.floor(this.performance.audience / 5);
  }
}

export default function createStatementData(invoice, plays) {
  const statementData = {};
  statementData.customer = invoice.customer; // 고객데이터를 중간 데이터로 옮김
  statementData.performances = invoice.performances.map(enrichPerformance);
  statementData.totalAmount = totalAmount(statementData);
  statementData.totalVolumeCredits = totalVolumeCredits(statementData);
  return statementData;

  function enrichPerformance(aPerformance) {
    // 각각 공연별로 이름, 총금액, 총포인트들을 새로할당
    const calculator = createPerformanceCalculator(
      aPerformance,
      playFor(aPerformance)
    );
    const result = Object.assign({}, aPerformance);
    result.play = playFor(result);
    result.amount = calculator.amount;
    result.volumeCredits = calculator.volumeCredits;
    return result; // 얕은복사
  }

  function createPerformanceCalculator(aPerformance, aPlay) {
    switch (aPlay.type) {
      case "tragedy":
        return new TragedyCalculator(aPerformance, aPlay);
      case "comedy":
        return new ComedyCalculator(aPerformance, aPlay);
      default:
        throw new Error(`알 수 없는 장르: ${aPlay.type}`);
    }
  }
  // 타입 (tragedy, comedy)
  function playFor(aPerformance) {
    return plays[aPerformance.playID];
  }

  function totalVolumeCredits(data) {
    return data.performances.reduce((total, p) => total + p.volumeCredits, 0);
  }

  function totalAmount(data) {
    return data.performances.reduce((total, p) => total + p.amount, 0);
  }
}

import INVOICE from "../../invoices.json";
import PLAYS from "../../plays.json";
import createStatementData from "./createStatementData.js";

function statement(invoice, plays) {
  // 가변데이터로 넘기면 금방 상하기때문에 최대한 불변으로 넘긴다. (굿)
  return renderPlainText(createStatementData(invoice, plays));
}

function renderPlainText(data, plays) {
  let result = `청구 내역(고객명: ${data.customer})\n`;
  for (let perf of data.performances) {
    // 청구 내역을 출력한다.
    result += `${perf.play.name}: ${usd(perf.amount)} (${perf.audience}석)\n`;
  }
  result += `총액: ${usd(data.totalAmount)}\n`;
  result += `적립 포인트: ${data.totalVolumeCredits}점\n`;
  return result;
}

function htmlStatement(invoice, plays) {
  return renderHtml(createStatementData(invoice, plays));
}

function renderHtml(data) {
  let result = `<h1>청구 내역(고객명: ${data.customer})</h1>\n`;
  result += `<table>\n`;
  result += `<tr><th>연극</th><th>좌석 수</th><th>금액</th></tr>`;
  for (let perf of data.performances) {
    // 청구 내역을 출력한다.
    result += `<tr><td>${perf.play.name}</td><td>(${perf.audience}석)</td>`;
    result += `<td>${usd(perf.amount)}</td></tr>\n`;
  }
  result += `</table>\n`;
  result += `총액: ${usd(data.totalAmount)}\n`;
  result += `적립 포인트: ${data.totalVolumeCredits}점\n`;
  return result;
}
function usd(aNumber) {
  return new Intl.NumberFormat("en-US", {
    style: "currency",
    currency: "USD",
    minimumFractionDigits: 2
  }).format(aNumber / 100);
}

document.getElementById("app2").innerText = statement(INVOICE[0], PLAYS);
document.getElementById("app").innerHTML = htmlStatement(INVOICE[0], PLAYS);