From 0570b0f580fd67e655a4af3cc6d7e075a732af30 Mon Sep 17 00:00:00 2001
From: dodonki1223 <make.an.effort.wish.come.true@gmail.com>
Date: Tue, 7 Dec 2021 08:56:16 +0900
Subject: [PATCH] =?UTF-8?q?:recycle:=20=E3=80=90=E7=AC=AC2=E7=AB=A0=20?=
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イミュータブルを意識して Dollar オブジェクトを返す実装に変更する
---
 TODO.md                      | 2 +-
 src/__tests__/dollar.test.ts | 7 +++----
 src/dollar.ts                | 5 +----
 3 files changed, 5 insertions(+), 9 deletions(-)

diff --git a/TODO.md b/TODO.md
index 7120148..81b4cb2 100644
--- a/TODO.md
+++ b/TODO.md
@@ -1,5 +1,5 @@
 - [ ] $5 + 10 CHF = $10(レートが 2:1 の場合)
 - [x] $5 * 2 = $10
 - [ ] amount を private にする
-- [ ] Dollar の副作用どうする？
+- [x] Dollar の副作用どうする？
 - [ ] Money の丸め処理どうする？
diff --git a/src/__tests__/dollar.test.ts b/src/__tests__/dollar.test.ts
index 5eed2c4..64edee9 100644
--- a/src/__tests__/dollar.test.ts
+++ b/src/__tests__/dollar.test.ts
@@ -2,8 +2,7 @@ import { Dollar } from '../dollar';
 
 test('times', () => {
   const five = new Dollar(5);
-  five.times(2)
-  expect(five.amount).toBe(10);
-  five.times(3)
-  expect(five.amount).toBe(15);
+  
+  expect(five.times(2).amount).toBe(10);
+  expect(five.times(3).amount).toBe(15);
 });
diff --git a/src/dollar.ts b/src/dollar.ts
index 25d57b9..7bdfd5f 100644
--- a/src/dollar.ts
+++ b/src/dollar.ts
@@ -1,12 +1,9 @@
 export class Dollar {
-  private tmpAmount: number
-
   constructor(public amount: number) {
-    this.tmpAmount = amount
     this.amount = amount
   }
 
   times(multiplier: number) {
-    this.amount = this.tmpAmount * multiplier
+    return new Dollar(this.amount * multiplier)
   }
 }