Learn Go: Functions

When a Go function parameter is passed by value, it means only a copy of the value is accessed and manipulated inside the function. The original value of the variable that is passed as an argument to the function remains intact.

func makeMeOlder(age int) {
  age += 5
}

func main() {
  myAge := 10
  makeMeOlder(myAge)
  fmt.Println(myAge)
  // myAge is still 10
}

A Go variable occupies a slot in virtual memory and is accessible via an address. To access the address of a variable, type & followed by the variable name. The value of a variable address is in the form of a hexadecimal number, such as 0x414020.

name := "Codecademy"
fmt.Printf("Address of %v is %v", name, &name)
// Address of Codecademy is 0xc000010210

The * operator preceding a data type is describing the data type for a Go pointer. For example:

var pointerToInt *int 
// a pointer to a variable of type int

The * operator preceding a variable is used to dereference a pointer variable. For example, the pointer variable, x, is assigned the address of variable, y. We dereference x by typing *x. By doing so, we can access and change the value of y. For example:

y := 3
var x *int = &y
*x = 5
fmt.Println(y) 
// y is now 5