February 2014
Intermediate to advanced
248 pages
4h 23m
Japanese
Content preview from 実践 Vagrant
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138
7 章 プラグインによる Vagrant の拡張
な
Ruby
のコードに過ぎないので、見ればわかることでしょう。どちらの設定オブ
ジェクトも同じ構造を持っていると考えることができるので、
instance_variable_
get
と
instance_variable_set
は自由に使うことができます。
これで設定のマージは終わりです。ほとんどの場合、デフォルトのマージ処理のロ
ジックで事は足りるはずであり、単純なルールを守って
UNSET_VALUE
を使えば、デ
フォルトのロジックは完璧に動作します。とはいえ、マージ処理のロジックを厳密に
制御する必要がある場合には、そうすることもできるのです。
プライベート変数と設定のマージ処理
場合によっては、設定の実装がその状態を追跡するインスタンス変数が、一
時的でマージされることを意図していないことがあります。2 重のアンダー
スコア（__ ）で始まるインスタンス変数が見つかった場合、Vagrant はそ
の変数を無視します。
このトリックは、カスタムのマージ処理のロジックの適用に先立って行われ
るデフォルトのマージのロジック（カスタムの
merge
メソッドの
super
の呼
び出しで行われます）で、コストのかかるオブジェクトのコピーを避けるた
めに広く使われます。
たとえば、Vagrant のコアは同期フォルダを
@__synced_folders
というイ
ンスタンス変数で追跡していますが、マージのロジックはカスタムなので、
こうすることで大きなハッシュが大量にコピーされることを避けているので ...
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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.