Pointers

Pointers in Go are an essential feature that allows working directly with a program’s memory. A pointer stores the memory address of another variable. This can be useful for accessing and modifying the value stored at that specific memory address.

Pointer Declaration

In Go, a pointer is declared using the dereferencing operator (*) before the data type to indicate that the variable is a pointer to that type of data. Then, to assign it the memory address of another variable, the & operator is used:

var x int = 7
var ptr *int = &x

fmt.Println(ptr)

The output for the above code contains the memory address that the pointer is pointing to:

0xc000096068

In this example, ptr is a pointer to an integer (*int) that stores the memory address of the variable x.

Accessing Values Through a Pointer

To access the value stored at the memory address pointed to by a pointer, the * operator is used:

var x int = 7
var ptr *int = &x

fmt.Println(*ptr)

The above code will print the value stored at the memory address pointed to by ptr:

7

Modifying Values Through a Pointer

Pointers allow developers to indirectly modify the value of a variable by accessing the memory address of that variable:

var x int = 7
var ptr *int = &x

*ptr = 10

This will change the value of the variable x to 10, as ptr points to the memory address of x:

10

Checking for Null Pointers

In Go, pointers are automatically initialized with the null value (nil). It’s important to check if a pointer is null before attempting to access the value it points to. Attempting to dereference a null pointer will result in a runtime panic, which may cause the program to stop abruptly:

var ptr *int

fmt.Println(ptr)

The output for the above code is:

<nil>

Example

Here’s a comprehensive example that declares, initializes, accesses, and modifies values through pointers in Go:

package main

import "fmt"

func main() {
  x := 7
  var ptr *int = &x

  fmt.Println("Value of x:", x)
  fmt.Println("Memory address of x:", ptr)
  fmt.Println("Value pointed by ptr:", *ptr)

  *ptr = 10
  fmt.Println("New value of x:", x)
}

The output for the above code is:

Value of x: 7
Memory address of x: 0xc00000a0f8
Value pointed by ptr: 7
New value of x: 10