June 2022
Beginner to intermediate
672 pages
17h 23m
Japanese
Content preview from Head Firstデザインパターン 第2版 ―頭とからだで覚えるデザインパターンの基本
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4
1
章
ジョーはこの方法
を、再利用のため
の継承の素晴らし
い使い方だと考え
ましたが、保守の
観点ではあまり適
切ではありません
でした。
なるほど、設計にちょっと不
備があったみたいだね。でも、
なんでそれが「機能」だと思え
ないのかな。かわいらしい
のに。
ジョーは、
Duck
には飛ばないサブク
ラスもあることに気付きませんでした。
ジョーが
Duck
スーパークラスに新しい振
る舞いを追加した際に、一部の
Duck
サブ
クラスには適切ではない振る舞いも追加し
てしまいました。その結果、
SimUDuck
プ
ログラムに空飛ぶ無生物を追加してしまっ
たのです。
コードを局所的に更新することで、非局
所的な副作用（空飛ぶゴムのアヒル）が発
生してしまいました！
何が起こったのでしょうか？
quack()
swim()
display
()
fly()
//
カモに関する他のメソッド
display() {
//
マガモ（
mallard
）
//
の表示
}
MallardDuck
display() {
//
アメリカホシハジロ
//
（
redhead
）の表示
}
RedheadDuck
quack() {
//
オーバーライドして
//
キューキューという音
//
（
Squeak
）にする
}
display() {
//
ゴムのアヒルの表示
}
RubberDuck
Duck
ゴムのアヒルはガーガー鳴く
（
quack
）ことはないため、
quack()
をオーバーライドし
て「キューキューという音
（
Squeak
）」にします。
スーパークラスに
fly()
を追加したので、飛ぶ
べきではないカモも含 ...
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O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.