How to call a function in Go based on attribute change?

[bvrygud (Good Boy)]

import (
	"fmt"
	"sync"
)

type BasketType int

const (
	_           BasketType = iota
	LARGEBASKET            //Holds max of 20 balls
	HUGEBASKET             //Holds unlimited balls
)

type Ball struct {
	Name     string //RubberBall, TennisBall etc
	Quantity int
	basket   BasketType
	once     sync.Once
	BasketLocator
}

func (ball *Ball) GetBasket() BasketType {
	ball.once.Do(func() { ball.LocateBasket(ball) })
	//fmt.Println("Basket in GetBasket", ball.basket)
	return ball.basket
}

type BasketLocator interface {
	LocateBasket(ball *Ball)
}

type BasketLocatorImpl struct {
}

func (locator BasketLocatorImpl) LocateBasket(ball *Ball) {
	fmt.Println("Calling basketlocator")
	if ball.Quantity < 20 {
		//fmt.Println("Setting large basket")
		ball.basket = LARGEBASKET
		return
	}
	//fmt.Println("Seting huge basket")
	ball.basket = HUGEBASKET
}

func main() {
	ball := Ball{
		Name:          "Tennis Ball",
		Quantity:      2,
		BasketLocator: BasketLocatorImpl{},
	}

	fmt.Println("Basket after first try ", ball.GetBasket())
	ball.Quantity = 10
	fmt.Println("Basket after second try ", ball.GetBasket())
	ball.Quantity = 30
	fmt.Println("Basket after thrid try ", ball.GetBasket())
}

In the above code, I am making sure that, we don’t unnecessarily call the LocateBasket function. It is called only once during the GetBasketCall. But if there is any attribute change (For eg. The quantity was changed to 30) then I wanted to make sure that when user calls GetBasket it internally calls LocateBasket function too.

In my example I had only one function, but if there is multiple attributes which needs to be re-calculated (based on attribute change) when their corresponding Getter Functions are getting called, what is the best approach to do the same.

[riking]

Well, basket is a private variable, no? So create a setBasket or SetBasket function that keeps everything in sync, or keep everything consistent everywhere you modify the variable.

[bvrygud (Good Boy)]

Thanks for the suggestion. But the problem with this approach is that it if there is multiple parameters , for eg. tomorrow if we have a new function “GetBasketColor()” which also needs to be changed based on the attribute - quantity then I have to implement the same logic in the other function too. And it becomes kind of redundant.