Why isn't my Stringer interface method getting invoked? When using fmt.Println

Question

Suppose I have the following code:

package main

import \"fmt\"

type Car struct{
    year int
    make string
}

func (c *Car)String() string{
    return fm         


        

Answer 1

Methods

Pointers vs. Values

The rule about pointers vs. values for receivers is that value methods can be invoked on pointers and values, but pointer methods can only be invoked on pointers. This is because pointer methods can modify the receiver; invoking them on a copy of the value would cause those modifications to be discarded.

Therefore, for your String method to work when invoked on both pointers and values, use a value receiver. For example,

package main

import "fmt"

type Car struct {
    year int
    make string
}

func (c Car) String() string {
    return fmt.Sprintf("{make:%s, year:%d}", c.make, c.year)
}

func main() {
    myCar := Car{year: 1996, make: "Toyota"}
    fmt.Println(myCar)
    fmt.Println(&myCar)
}

Output:

{make:Toyota, year:1996}
{make:Toyota, year:1996}