✨ 【第8章 実装を隠す】 times の一般化手前まで実装する

・TypeScriptの循環参照でエラーになるため Dollar と Franc の実装を一旦 Money クラスに寄せる

TODO.md

@@ -12,3 +12,4 @@
 - [x] equalsの一般化
 - [ ] timesの一般化
 - [x] FrancとDollarの比較
+- [ ] 通貨の概念

src/__tests__/dollar.test.ts

@@ -1,8 +1,9 @@
-import { Dollar } from '../dollar';
+// import { Dollar } from '../dollar';
+import { Money, Dollar } from '../money';
 
 test('times', () => {
-  const five = new Dollar(5);
-  
+  const five: Money = Money.dollar(5);
+
   expect(five.times(2)).toEqual(new Dollar(10));
   expect(five.times(3)).toEqual(new Dollar(15));
 });

src/__tests__/franc.test.ts

@@ -1,8 +1,10 @@
-import { Franc } from '../franc';
+// import { Franc } from '../franc';
+import { Money, Franc } from '../money';
 
 test('times', () => {
-  const five = new Franc(5);
+  const five: Money = Money.franc(5);
 
   expect(five.times(2)).toEqual(new Franc(10));
   expect(five.times(3)).toEqual(new Franc(15));
 });
+

src/__tests__/money.test.ts

@@ -1,20 +1,23 @@
-import { Dollar } from '../dollar';
-import { Franc } from '../franc';
-import { Money } from '../money';
+// import { Dollar } from '../dollar';
+// import { Franc } from '../franc';
+import { Money, Dollar, Franc } from '../money';
 
 test('equals', () => {
-  expect(new Money(5).equals(new Money(5))).toBeTruthy();
-  expect(new Money(5).equals(new Money(6))).toBeFalsy();
+  expect(new Franc(5).equals(new Franc(5))).toBeTruthy();
+  expect(new Franc(5).equals(new Franc(6))).toBeFalsy();
+  expect(new Dollar(5).equals(new Dollar(5))).toBeTruthy();
+  expect(new Dollar(5).equals(new Dollar(6))).toBeFalsy();
 });
 
 test('null equals', () => {
-  const five = new Money(5);
+  const francFive = new Franc(5);
+  expect(francFive.equals(null)).toBeFalsy();
 
-  expect(five.equals(null)).toBeFalsy();
+  const dollarFive = new Dollar(6);
+  expect(dollarFive.equals(null)).toBeFalsy();
 });
 
 test('equals Franc = Dollar', () => {
   expect(new Franc(5).equals(new Dollar(5))).toBeTruthy();
   expect(new Franc(5).equals(new Dollar(6))).toBeFalsy();
 });
-

src/dollar.ts

@@ -1,11 +1,11 @@
-import { Money } from "./money";
+// import { Money } from "./money";
 
-export class Dollar extends Money {
-  constructor(amount: number) {
-    super(amount);
-  }
+// export class Dollar extends Money {
+//   constructor(amount: number) {
+//     super(amount);
+//   }
 
-  times(multiplier: number) {
-    return new Dollar(this.amount * multiplier)
-  }
-}
+//   times(multiplier: number) {
+//     return new Dollar(this.amount * multiplier)
+//   }
+// }

src/franc.ts

@@ -1,11 +1,11 @@
-import { Money } from "./money";
+// import { Money } from "./money";
 
-export class Franc extends Money {
-  constructor(amount: number) {
-    super(amount);
-  }
+// export class Franc extends Money {
+//   constructor(amount: number) {
+//     super(amount);
+//   }
 
-  times(multiplier: number) {
-    return new Franc(this.amount * multiplier)
-  }
-}
+//   times(multiplier: number) {
+//     return new Franc(this.amount * multiplier)
+//   }
+// }

src/money.ts

@@ -1,7 +1,20 @@
-export class Money {
+// import { Dollar } from "./dollar";
+// import { Franc } from "./franc";
+
+export abstract class Money {
   constructor(protected readonly amount: number) {
   }
 
+  static dollar(amount: number):Dollar {
+    return new Dollar(amount)
+  }
+
+  static franc(amount: number):Franc {
+    return new Franc(amount)
+  }
+
+  abstract times(multiplier: number): Money
+
   equals(money: Money | null) {
     if (money === null) {
         return false;
@@ -10,3 +23,23 @@ export class Money {
     return this.amount === money.amount
   }
 }
+
+export class Dollar extends Money {
+  constructor(amount: number) {
+    super(amount);
+  }
+
+  times(multiplier: number): Money {
+    return new Dollar(this.amount * multiplier)
+  }
+}
+
+export class Franc extends Money {
+  constructor(amount: number) {
+    super(amount);
+  }
+
+  times(multiplier: number): Money {
+    return new Franc(this.amount * multiplier)
+  }
+}