每个Person都可以发送命令，每个命令对应着人和动作

package main


import "fmt"


// 每个Person都可以发送命令，每个命令对应着人和动作
// 如王五可以向李四发送听取指令的命令
// 李四可以向张三发送买东西的指令


type Person struct {
    name string
    cmd  Command
}


type Command struct {
    person *Person
    method func()
}


func NewCommand(p *Person, method func()) Command {
    return Command{
        person: p,
        method: method,
    }
}


func (c *Command) Execute() {
    if c.method == nil {
        return
    }
    c.method()
}


func NewPerson(name string, cmd Command) Person {
    return Person{
        name: name,
        cmd:  cmd,
    }
}


func (p *Person) Buy() {
    fmt.Printf("%s is buying\n", p.name)
    p.cmd.Execute()
}


func (p *Person) Cook() {
    fmt.Printf("%s is cooking\n", p.name)
    p.cmd.Execute()
}


func (p *Person) Wash() {
    fmt.Printf("%s is washing\n", p.name)
    p.cmd.Execute()
}


func (p *Person) Listen() {
    fmt.Printf("%s is listening\n", p.name)
    p.cmd.Execute()
}


func (p *Person) Talk() {
    fmt.Printf("%s is talking\n", p.name)
    p.cmd.Execute()
}


func main() {
    zhangsan := NewPerson("张三", NewCommand(nil, nil))
    lisi := NewPerson("李四", NewCommand(&zhangsan, zhangsan.Buy))
    wangwu := NewPerson("王五", NewCommand(&lisi, lisi.Listen))


    wangwu.Talk()


}