solution to interview task

buyandsell_solution2.go

package main

import (
	"fmt"
)

type Cement struct {
	NoOfCement int
}

func (c *Cement) BuyCement(howmany int) {
	c.NoOfCement += howmany
}

func (c *Cement) SellCement(howmany int) {
	c.NoOfCement -= howmany // o was undefined here.
}

func (c Cement) String() string {    //Cement is now passed by value here
	return fmt.Sprintf("%v", c.NoOfCement)
}

func main() {
	var cement Cement
	cement.BuyCement(15)
	cement.SellCement(9)
	fmt.Println(cement)   
}

buyandsell_solution_1.go

package main

import (
	"fmt"
)

type Cement struct {
	NoOfCement int
}

func (c *Cement) BuyCement(howmany int) {
	c.NoOfCement += howmany
}

func (c *Cement) SellCement(howmany int) {
	c.NoOfCement -= howmany // o is undefined here.
}

func (c *Cement) String() string {    //Cement is now passed by reference here
	return fmt.Sprintf("%v", c.NoOfCement)
}

func main() {
	var cement Cement
	cement.BuyCement(15)
	cement.SellCement(9)
  fmt.Println(&cement)    //to call the (* Cement)String here, you have to pass the pointer to Cement
}