组合模式统一对象和对象集，使得使用相同接口使用对象和对象集。
组合模式常用于树状结构，用于统一叶子节点和树节点的访问，并且可以用于应用某一操作到所有子节点。
composite.go
package composite
import "fmt"
type Component interface {
Parent() Component
SetParent(Component)
Name() string
SetName(string)
AddChild(Component)
Print(string)
}
const (
LeafNode = iota
CompositeNode
)
func NewComponent(kind int, name string) Component {
var c Component
switch kind {
case LeafNode:
c = NewLeaf()
case CompositeNode:
c = NewComposite()
}
c.SetName(name)
return c
}
type component struct {
parent Component
name string
}
func (c *component) Parent() Component {
return c.parent
}
func (c *component) SetParent(parent Component) {
c.parent = parent
}
func (c *component) Name() string {
return c.name
}
func (c *component) SetName(name string) {
c.name = name
}
func (c *component) AddChild(Component) {}
func (c *component) Print(string) {}
type Leaf struct {
component
}
func NewLeaf() *Leaf {
return &Leaf{}
}
func (c *Leaf) Print(pre string) {
fmt.Printf("%s-%s\n", pre, c.Name())
}
type Composite struct {
component
childs []Component
}
func NewComposite() *Composite {
return &Composite{
childs: make([]Component, 0),
}
}
func (c *Composite) AddChild(child Component) {
child.SetParent(c)
c.childs = append(c.childs, child)
}
func (c *Composite) Print(pre string) {
fmt.Printf("%s+%s\n", pre, c.Name())
pre += " "
for _, comp := range c.childs {
comp.Print(pre)
}
}
composite_test.go
package composite
func ExampleComposite() {
root := NewComponent(CompositeNode, "root")
c1 := NewComponent(CompositeNode, "c1")
c2 := NewComponent(CompositeNode, "c2")
c3 := NewComponent(CompositeNode, "c3")
l1 := NewComponent(LeafNode, "l1")
l2 := NewComponent(LeafNode, "l2")
l3 := NewComponent(LeafNode, "l3")
root.AddChild(c1)
root.AddChild(c2)
c1.AddChild(c3)
c1.AddChild(l1)
c2.AddChild(l2)
c2.AddChild(l3)
root.Print("")
// Output:
// +root
// +c1
// +c3
// -l1
// +c2
// -l2
// -l3
}