What is the difference between these object instantiation methods?

[Feoggou]

What is the difference between these object instantiation methods:

1.

ClassName ObjectName;

2.

ClassName ObjectName();

Is there any?

[laserlight]

The latter declares a function that takes no arguments and returns a ClassName.

[Paul McKenzie]

What is the difference between these object instantiation methods:

There is no instantiation going on in the second method. That's a function declaration.

See here:

#include <string>

int main()

struct ClassName
{
};

ClassName ObjectName();  // declare function

int main()
{
    ClassName theName;
    theName = ObjectName();
}


// here is the function impelemtation
ClassName ObjectName()
{
   return ClassName();
}

See the code in red?

Regards,

Paul McKenzie

[jnmacd]

http://www.parashift.com/c++-faq-lit....html#faq-10.2

[Feoggou]

thanks a lot.

It seems that if you have a class defined like this:

class ClassName
{
     int x;
public:
    ClassName()
   {
       x = 3;
   }
};

you can use either this:

ClassName obj;

or this:

ClassName obj();

And I was saying to myself: there can't be any difference!