package main

import "fmt"

type Counter struct {
	value int
}

// pointer receiver. The method operates directly on the object c points to
// Use a pointer receiver whenever the object needs to be modified.
func (c *Counter) Increment() {
	c.value++
}

// value receiver. The method operates on copy of object c. Use a value
// receiver when the object does not need to be modified in the method.
func (c Counter) String() string {
	return fmt.Sprintf("Counter value: %d", c.value)
}

func main() {
	c := Counter{}
	fmt.Println(c)
	c.Increment()
	fmt.Println(c)
}