Used in this article: https://medium.com/@bgoetzmann/modèle-de-conception-commande-en-langage-groovy-9bea26b47d6

CommandDesignPattern.groovy

class Item {
    String name
    Double price
}

class Cart {
    Map items = [:]

    Cart addItem(Item item) {
        items[item.name] = item
        this
    }
    
    Cart removeItem(Item item) {
        items.remove(item.name)
        this
    }
}

trait CartCommand {
    Cart cart
    abstract def execute()
}

class AddItemCommand implements CartCommand {
    Item item
    
    AddItemCommand(Cart cart, Item item) {
        this.cart = cart
        this.item = item
    }

    def execute() {
        cart.addItem(item)
    }
}

class RemoveItemCommand implements CartCommand {
    Item item
    
    RemoveItemCommand(Cart cart, Item item) {
        this.cart = cart
        this.item = item
    }

    def execute() {
        cart.removeItem(item)
    }
}

def cart = new Cart()

// Command object creation
def command1 = new AddItemCommand(cart, new Item(name: 'Item1', price: 1))
def command2 = new AddItemCommand(cart, new Item(name: 'Item2', price: 1))
def command3 = new RemoveItemCommand(cart, new Item(name: 'Item1', price: 1))

// Invoke commands (invoker part)
def commands = [command1, command2, command3]
commands*.execute()

assert cart.items.keySet() == ['Item2'] as Set