How to create an object in a form like this: ifstream in();

Question

Im beginner in c++. I have seen several times when object created like:

class_name object_name();

and after that you can refer to object_name as an object of the class. How can i do this in my class? Should I override the constructor? And how to do that?

I think you need to show us a bit more of what you have in mind in order for us to offer an answer or even much in the way of useful commentary. — user4581301, Apr 09 '22 at 08:04
Where did you see a variable definition in the form `ifstream in();`? — πάντα ῥεῖ, Apr 09 '22 at 08:04
You have never seen an object created in that way. I would recommend that you start [here](https://stackoverflow.com/questions/388242/the-definitive-c-book-guide-and-list). — molbdnilo, Apr 09 '22 at 08:15

einpoklum · Accepted Answer · 2022-04-09T14:36:56.613

1

This line of code can probably trigger a vexing (but not "the most vexing") parse behavior: instead of being interpreted as a variable declaration, it will be interpreted as the declaration of a function named object_name, taking no parameters and returning a value of type class_name.

See it happen on GodBolt: The compiler tells you:

<source>: In function 'void foo()':
<source>:4:27: warning: empty parentheses were disambiguated as a function declaration [-Wvexing-parse]
    4 |     class_name object_name();
      |

edited Apr 09 '22 at 14:36

answered Apr 09 '22 at 08:06

einpoklum

118,144
57
340
684

@PeteBecker: You're right. This is just a vexing parse. – einpoklum Apr 09 '22 at 14:36

How to create an object in a form like this: ifstream in();

1 Answers1

Linked

Related