c++ expression must have class type

Question

Problem:

I've got a problem with c++ code. I am attaching the sample code snippet below. Please pull me up. Yee, of course, I am pretty new  in C++

#include <iostream>
using namespace std;

class Myclass
{
  public:
    void myfunc() {
      cout<<"Hello World"<<endl;
    }
};

int main()
{
  // A pointer to our class is created. 
  Myclass *a = new Myclass();
  // myfunc is part of the class object, rather than
  // part of the pointer to that class' object.
  a.myfunc(); 
}

 

Answer 1

The code snippet you attached is tried to apply the . operator on a pointer to an object, rather than on an object itself. That is the reason the code throws an "expression must have class type"​ error.

You should write this way:

 

#include <iostream>
using namespace std;

class Myclass
{
  public:
    void myfunc() {
      cout<<"Hello World"<<endl;
    }
};

int main()
{
  // A class object of Myclass is created. 
  Myclass a ;
  // The . operator is used to access the class' methods.
  a.myfunc(); 
}

I hope you get it.

Answer 2

The “expression should have class type” is an error that is thrown at the time the . operator, which is generally applied to access an object’s fields and methods, is used on pointers to objects.

At the time applied on a pointer to an object, the . operator will attempt to trace the pointer’s fields or systems, however it won’t, since they do not subsist. These fields or methods are part of an object, more than a part of the pointer to an object.

Wrong code

The code below attempts to imbed the . operator on a pointer to an object, more than on an object itself. The code throws an "expression should have class type"​ error.

using namespace std;
class Myclass
{
  public:
    void myfunc() {
      cout<<"Hello World"<<endl;
    }
};
int main()
{
  // A pointer to our class is created. 
  Myclass *a = new Myclass();
  // myfunc is part of the class object, rather than
  // part of the pointer to that class' object.
  a.myfunc(); 
}#include <iostream>

Correct code

The code below accurately embeds the . operator on an object to access the object’s member functions. Because a is now a class object, the code does not throw any error.

#include <iostream>
using namespace std;
class Myclass
{
  public:
    void myfunc() {
      cout<<"Hello World"<<endl;
    }
};
int main()
{
  // A class object of Myclass is created. 
  Myclass a ;
  // The . operator is used to access the class' methods.
  a.myfunc(); 
}