haru-s https://blog.hatena.ne.jp/haru-s/ ...ing logging 4.0 https://haru-s.hatenablog.com/ D言語 入れ物と中身を同一視するパターン． import std.stdio; interface Element { uint countChilds(); void append(Element c); } class Folder : Element { private Element[] elems; override uint countChilds() { uint sum; foreach (c; elems) { sum += 1 + c.countChilds(); } return sum; } override void append(Element c) { elems ~= … 190 <iframe src="https://hatenablog-parts.com/embed?url=https%3A%2F%2Fharu-s.hatenablog.com%2Fentry%2F20101103%2F1288776608" title="Composite pattern - ...ing logging 4.0" class="embed-card embed-blogcard" scrolling="no" frameborder="0" style="display: block; width: 100%; height: 190px; max-width: 500px; margin: 10px 0px;"></iframe> Hatena Blog https://hatena.blog 2010-11-03 18:30:08 rich https://haru-s.hatenablog.com/entry/20101103/1288776608 1.0 100%