CODESAMPLE

Command - Go

Command Go

The Command pattern encapsulates a request as an object, allowing for parameterization of clients with different requests, queuing or logging of requests, and support for undoable operations. This example defines a Command interface with an Execute method. Concrete commands like BuyCommand and SellCommand implement this interface, holding the necessary data to perform the action on a StockTrader receiver. An Invoker (broker) manages the commands and executes them. This Go implementation uses interfaces to define the command structure, making it flexible and testable, and aligns with Go’s preference for composition over inheritance.

// main.go
package main

import "fmt"

// Command interface
type Command interface {
	Execute()
}

// StockTrader receiver
type StockTrader struct {
	cash int
	shares int
}

func (s *StockTrader) Buy(quantity, price int) {
	cost := quantity * price
	if s.cash >= cost {
		s.cash -= cost
		s.shares += quantity
		fmt.Printf("Bought %d shares at %d. Cash: %d, Shares: %d\n", quantity, price, s.cash, s.shares)
	} else {
		fmt.Println("Insufficient funds")
	}
}

func (s *StockTrader) Sell(quantity, price int) {
	if s.shares >= quantity {
		s.cash += quantity * price
		s.shares -= quantity
		fmt.Printf("Sold %d shares at %d. Cash: %d, Shares: %d\n", quantity, price, s.cash, s.shares)
	} else {
		fmt.Println("Insufficient shares")
	}
}

// Concrete Commands
type BuyCommand struct {
	trader   *StockTrader
	quantity int
	price    int
}

func (b *BuyCommand) Execute() {
	b.trader.Buy(b.quantity, b.price)
}

type SellCommand struct {
	trader   *StockTrader
	quantity int
	price    int
}

func (s *SellCommand) Execute() {
	s.trader.Sell(s.quantity, s.price)
}

// Invoker / Broker
type Broker struct {
	commands []Command
}

func (b *Broker) AddCommand(command Command) {
	b.commands = append(b.commands, command)
}

func (b *Broker) ExecuteCommands() {
	for _, command := range b.commands {
		command.Execute()
	}
}

func main() {
	trader := &StockTrader{cash: 1000, shares: 0}
	broker := &Broker{}

	broker.AddCommand(&BuyCommand{trader: trader, quantity: 10, price: 50})
	broker.AddCommand(&SellCommand{trader: trader, quantity: 5, price: 60})
	broker.AddCommand(&BuyCommand{trader: trader, quantity: 20, price: 40}) // Might fail

	broker.ExecuteCommands()
}