8. 组合模式（Composite）

8. 组合模式（Composite）

问题：想统一对待单个对象和组合对象（如文件与文件夹）。

核心：定义统一接口，叶子和容器都实现它，容器递归调用子元素。

class File {
  constructor(name) { this.name = name; }
  display(indent = '') { console.log(`${indent}- ${this.name}`); }
}

class Folder {
  constructor(name) { this.name = name; this.children = []; }
  add(child) { this.children.push(child); return this; }
  display(indent = '') {
    console.log(`${indent}📁 ${this.name}`);
    this.children.forEach(c => c.display(indent + '  '));
  }
}

const root = new Folder('项目')
  .add(new File('index.js'))
  .add(new Folder('src').add(new File('app.js')).add(new File('utils.js')));

root.display();
// 📁 项目
//   - index.js
//   📁 src
//     - app.js
//     - utils.js
package composite

import "fmt"

type Component interface {
  Display(indent string)
}

type File struct{ Name string }

func (f File) Display(indent string) {
  fmt.Printf("%s- %s\n", indent, f.Name)
}

type Folder struct {
  Name     string
  Children []Component
}

func (f *Folder) Add(c Component) *Folder {
  f.Children = append(f.Children, c)
  return f
}

func (f *Folder) Display(indent string) {
  fmt.Printf("%s📁 %s\n", indent, f.Name)
  for _, child := range f.Children {
    child.Display(indent + "  ")
  }
}