Pointers in Go Programming

Welcome to part 4 of the Go programming tutorial series. In the previous tutorial, we covered some function basics. Now, we're going to cover the last basic concept before creating a simple web app, which is pointers. Pointers allow you to reference from memory, which lets you do some interesting things. Let's do a basic run-through.

We'll start by defining a variable:

package main

import "fmt"

func main() {
	x := 15
}

If we want to point to x, we can use the & symbol, like so:

a := &x

This gives us the memory address, so if we do:

fmt.Println(a)

This should output: 0xc0420441c0. We can read through pointers using * before the variable. For example:

package main

import "fmt"

func main() {
	
	x := 15

	a := &x         // point to x 
	fmt.Println(a)
	fmt.Println(*a)
	
}

Giving us:

0xc042008250
15

Okay, so what's the point of this? Well, what if we re-defined the reading through of a?

	*a = 5

The a variable was just a memory address, and the asterisk gets us to read through to the memory address, when we combine these two, we can actually modify the value at that memory address. Thus:

	fmt.Println(x)

Gives us: 5

So, what might happen with:

	*a = *a**a

Now what is the value of x? You shoudl be able to do it in your head. If not...

	fmt.Println(x)
	fmt.Println(*a)

Now, how might you get the memory address using x and a?

	fmt.Println(&x)
	fmt.Println(a)

Full code up to this point:

package main

import "fmt"

func main() {
	x := 15
	a := &x         // point to x  (memory address)
	fmt.Println(a)  // prints out the mem addr.
	fmt.Println(*a) // read a through the pointer, so this will print out a value (15 in this case)
	
	*a = 5          // sets the value pointed at to 5, which means x is modified (since x is stored at the mem addr)
	fmt.Println(x)  // see the new value of x
	*a = *a**a      // what is the value of x now? 
	fmt.Println(x)  // prints a value
	fmt.Println(*a) // prints a value

	fmt.Println(&x) // prints a memory address
	fmt.Println(a)      // prints a memory address
}

The next tutorial: Simple Web App in Go Programming