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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5
章
Singleton
パターン
you are here
177
Singleton
static uniqueInstance
//
他の便利な
Singleton
データ
static getInstance()
//
他の便利な
Singleton
メソッド
Singletonパターンは、クラスがインスタンスを
1
つしか持
たないことを保証し、そのインスタンスにアクセスするグ
ローバルポイントを提供する。
Singleton
パターンの定義
Singleton
の典型的な実装がわかったところで、少しくつろいでチョコレートバーで
も味わいながら、
Singleton
パターンの詳細について調べてみることにしましょう。
まず、パターンの簡潔な定義から始めましょう。
驚きはないでしょう。もう少しわかりやすく説明しましょう。
●
実際には何が起こっているのでしょうか。あるクラスにそのクラスのただ
1
つのインスタンスを管理させます。また、他のクラスが勝手に新規インスタ
ンスを作成できないようにもします。インスタンスを取得するには、そのク
ラス自体を経由します。
●
また、そのインスタンスに対するグローバルアクセスポイントを提供します。
つまり、インスタンスが必要になったときには、そのクラスに依頼するだけ
で
1
つのインスタンスが返ってきます。すでに説明したように、
Singleton
が
遅延方式で作成されるように実装できます。これは、リソース集約型のオブ
ジェクトにとっては非常に重要です。
ここでクラス図を見てみましょう。
getInstance() ...
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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.