April 2022
Beginner to intermediate
464 pages
6h 44m
Japanese
Content preview from 実用 Go言語 ―システム開発の現場で知っておきたいアドバイス
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3.4 構造体の埋め込みで共通部分を使いまわす
これまで構造体の基本的な定義の仕方、メソッドの定義について紹介しました。この中で、複数の階層を持った構造体の作り方も紹介しました。
これとは別に、多くのモデル構造体を作成するときなど、複数階層ではなく1つの階層で共通部分を使いまわしたいことがあります。そのようなニーズに対するソリューションとして、Goは構造体の埋め込みを提供しています1。
埋め込みには、名前をつけずに型だけを構造体のフィールドとして記述します。
type Book struct {
Title string
ISBN string
}
func (b Book) GetAmazonURL() string {
return "https://amazon.co.jp/dp/" + b.ISBN
}
type OreillyBook struct {
Book
ISBN13 string
}
func (o OreillyBook) GetOreillyURL() string {
return "https://www.oreilly.co.jp/books/" + o.ISBN13 + "/"
}
OreillyBook構造体をこのように宣言すると、インスタンス利用時には埋め込んだBook構造体のフィールドが、あたかも一緒に宣言されたもののようにふるまいます。ただし「同じような」挙動をするのは、あくまでもフィールドの参照とメソッドを呼び出すインスタンスの利用時のみです。インスタンス作成時には型名と同名のフィールドが存在するように書く必要があります。
ob := OreillyBook{
ISBN13: "9784873119038",
Book:Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
and much more.
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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.