add composite

Author: senghoo

13_composite/README.md

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+# 组合模式
+
+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。

13_composite/composite.go

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+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)
+	}
+}

13_composite/composite_test.go

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+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
+}