package main

import "fmt"

type State struct {
    X int
}

type Command interface {
    Execute(state *State)
}

type MoveLeft struct {
    Command
}

func (c *MoveLeft) Execute(state *State) {
    state.X -= 1
}

type Executor interface {
    Execute(command Command)
}

type Dummy struct {
    State State
    Executor
}

func (d *Dummy) Execute(command Command) {
    command.Execute(&d.State)
}

func main() {
    foo := Dummy{State: State{X: 0}}
    fmt.Println(foo.State) // {0}

    // Cannot use 'MoveLeft{}' (type MoveLeft) as the type CommandType does
    // not implement 'Command' as the 'Execute' method has a pointer reciever
    //foo.Execute(MoveLeft{})

    // но по ссылке все гуд
    foo.Execute(&MoveLeft{})
    fmt.Println(foo.State) // {-1}
}