Value/Pointer Receiver

func (n Node) Name() string {...}   // Value Receiver     <-- creates a copy of the struct
func (n *Node) Name() string {...}  // Pointer Receiver   <-- doesn't create a copy

Function vs Method

A function is declared by specifying the types of the arguments, the return values, and the function body.

type Person struct {
    Name string
    Age  int
}

func NewPerson(name string, age int) *Person {
  return &Person{
     Name: name,
     Age:  age,
  }
}

A method is just a function with a receiver argument. It is declared with the same syntax with the addition of the receiver.

func (p *Person) isAdult bool {
  return p.Age > 18
}

Value receiver makes a copy of the type and passes it to the function. The function stack now holds an equal object but at a different location on memory. That means any changes done on the passed object will remain local to the method. The original object will remain unchanged.

Pointer receiver passes the address of a type to the function. The function stack has a reference to the original object. So any modifications on the passed object will modify the original object.

package main
import "fmt"
type Person struct {
    Name string
    Age  int
}
func ValueReceiver(p Person) {
    p.Name = "John"
    fmt.Println("Inside ValueReceiver : ", p.Name)
}
func PointerReceiver(p *Person) {
    p.Age = 24
    fmt.Println("Inside PointerReceiver model: ", p.Age)
}
func main() {
    p := Person{"Tom", 28}
    p1:= &Person{"Patric", 68}
    ValueReceiver(p)
    fmt.Println("Inside Main after value receiver : ", p.Name)
    PointerReceiver(p1)
    fmt.Println("Inside Main after value receiver : ", p1.Age)
}

// Inside ValueReceiver :  John
// Inside Main after value receiver :  Tom
// Inside PointerReceiver :  24
// Inside Main after pointer receiver :  24