Golang - Doubt about pointers

Question

I have a struct called Calculator, with two properties: version and author. To be able to instantiate this struct already initiating these methods, since Golang has no constructors, the various tips I found on the net indicate to create a Newcalculator() method and then use it to instantiate the calculator. The method would look like this:

func NewCalculadora() *Calculadora {
        return &Calculadora{autor:"Paulo Luvisoto",versao:1.0}
}

And all tips indicate the use of pointer, as above. But I saw that so also works:

func NewCalculadora() Calculadora {
        return Calculadora{autor:"Paulo Luvisoto",versao:1.0}
}

My question is: what is the problem of using this second way, without using pointer?

Answer 1

The best definition I’ve ever heard on this subject was this::

Pointers are for sharing.

Usually this doubt comes down to a question of semantics.

For example: You create a value of type Calculadora.

calc := NewCalculadora()

Okay, you’ve got your calculator (Calc).

Do you intend/need to change/change the values of this type? (author or version)

No? Then returning a copy is enough. Remember that in Go arguments are passed by value (copy).

In your case, if you want to change any of the fields of this type, you need a pointer.

A beautiful example of this is the package time.

See the function Time.Add, although you add a duration to an instant of time, you are not changing that "instance", but are returning a new value.

Going against the grain, the package os, has the type os. File which uses pointer semantics. Since in this case it is much more logical for you to share a file than to create copies.

So, there is no problem in using with or without pointer, everything will depend on what you intend to do. I hope this helps resolve your doubt.