CODEWITHSUNDEEP
c++classoopmacros
CheckYourSec
CheckYourSec

Reputation: 143

Call class function with macro

Here i want to call world function from class Hello with macro MPRINT() but it doesn't recognize the macro syntax:

#include <windows.h>
#include <iostream>
#include <string.h>

using namespace std;

// first try
#define MPRINT(text) \
    []() -> Hello::world(#text)\
    }()

// second try
#define MPRINT(text) \
Hello obj; \
obj.world(text);

class Hello
{
public:
    string world(string inp);
};

string Hello::world(string inp) {
    return inp + "|test";
}

int main()
{
    string test1 = MPRINT("blahblah"); // error "type name is not allowed"
    cout << MPRINT("blahblah"); // error "type name is not allowed"
    return 0;
}

Upvotes: 0

Views: 709

Answers (1)

cigien
cigien

Reputation: 60440

In your first attempt, you are trying to use Hello::world, but this is not the correct syntax for calling a non-static member function.

In your second attempt, using MPRINT would result in:

string test1 = Hello obj; obj.world(text); ;

which is also clearly invalid.

You could write the macro like this:

#define MPRINT(text)            \
    [] {                        \
       Hello obj;               \
       return obj.world(#text); \
    }()

Here's a demo.

That being said, I strongly suggest that you don't use macros for this sort of thing. The following function works perfectly well:

auto MPRINT(std::string text) 
{                        
  Hello obj;               
  return obj.world(text); 
};

Here's a demo.

Upvotes: 3

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