May 2019
Intermediate to advanced
464 pages
9h 22m
Japanese
Content preview from Node.jsデザインパターン 第2版
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6.9
ミドルウェア
191
ミドルウェアマネージャ
入力 出力
ミドルウェア
A
ミドルウェア
B
ミドルウェア
C
ミドルウェア
D
use()
図6-7 ミドルウェアパターン
このパターンに必須の構成要素が「ミドルウェアマネージャ」で、ミドルウェアの関数を組織立てて
実行する役割を担います。パターンの実装詳細でもっとも重要な点は次のとおりです。
●
新たなミドルウェアは関数
use()
を呼び出すことで登録される（この関数名は、このパターンの
数多くの実装に共通する慣習だが、任意の名前でかまわない）。通常、新たなミドルウェアはパ
イプラインの最後にしか追加できないが、これは厳密に守らねばならない規則ではない
●
処理が必要なデータを新しく受け付けた場合、登録されているミドルウェアは非同期の逐次実行
の流れとして起動される。パイプライン内の各ユニットが、前のユニットの実行結果を入力とし
て受け取る
●
ミドルウェアの各関数が、コールバックを起動しないか、コールバックにエラーを渡すことで、
その先のデータ処理を簡単に停止できる。エラーが起こると、通常はエラー処理に特化した一連
のミドルウェアがあって、その実行が始まる
パイプライン内でデータがどのように処理され伝播して行くかに関する厳密な規則はありません。実
装方法には次のようなものがあります。
●
追加の関数やプロパティでデータを補う
●
何らかの処理結果でデータを置き換える
●
データは変更不可能のままとし、処理の結果として必ず新規のコピーを返す
どれが正しい実装方法かは、ミドルウ
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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.