How to reassign in pointer method receiver?

Question

What I understand about pointer method receiver and non-pointer method receiver is first one can be modified in the method and next one isn't.

So, following worked exactly as I expected.
type student struct {
    name string
    age  int
}

func (s *student) update() {
    s.name = "unknown"
    s.age = 0
}

func main() {
    s := student{"hongseok", 13}
    fmt.Println(s)

    s.update()
    fmt.Println(s)
}

It prints hongseok/13 and unknown/0.

But, I want to replace whole s in update method at once with reassigning. So, I've just altered update method as bellow.
func (s *student) update() {
    s = &student{"unknown", 0}
}

And it doesn't change s in main method and prints double hongseok/13.
func (s *student) update() {
    *s = student{"unknown", 0}
}

Above change fix the problem.
I think there's no semantic difference. What am I missing?

Aditya Agrawal · Accepted Answer

In the first example: func (s *student) update() { s = &student{"unknown", 0} } You are assigning an entirely new "pointer value" to s, and the new *s points at a new student value. The variable s is scoped only to the method body, so there are no side effects after this returns. In the second example func (s *student) update() { *s = student{"unknown", 0} } You are dereferencing s, and changing the value of *s to point to a new student value, or to put it differently, you are putting a new student value at the address where s points.

Go Language

Similar Questions

How to return values from goroutines?

How to print struct variables in console?

How to crate for loop of two variables in Go?

On a mission to build Next-Gen Community Platform for Developers

Facebook

Twitter

Linkedin

Instagram