What is the difference between Object b(); and Object b;?

Question

To be more explicit, I get a compile time error when I try accessing an instance variable when I create an object using (), but when I don\'t, the code compiles and runs as expe

Answer 1

The problem is that Student jack(); declares a function with Student as a return type. It doesn't declare an object of that class as you expect.

Answer 2

  Student jack();

declares a function that returns student and takes no arguments. Not an object!

See more in this gotw

Answer 3

What is the difference between Object b(); and Object b;?

The difference exists because C++ interprets that as a function being declared, instead of an object being created.

Object b;

This is the object b of class Object being created by means of the default constructor.

Object b();

This is the function b(), being declared (it will be defined elsewhere) to return an object of class Object, and no parameters.

Hope this helps.

Answer 4

I would try this

class Student {

public:

int gpa = 4;

Student() { };

Answer 5

"Object b();" declares a function b() returning an object of type Object, while "Object b;" defines a variable b of type Object.

No, it's not obvious, and it still comes back to bite me if I switch between C++, Java, and C#. :-)