Compiling polygone.h
and polygone.cc
gives error:
polygone.cc:5:19: error: expected constructor, destructor, or type conversion before ‘(’ token
Code:
//polygone.h
# if !defined(__POLYGONE_H__)
# define __POLYGONE_H__
# include <iostream>
class Polygone {
public:
Polygone(){};
Polygone(std::string fichier);
};
# endif
and
//polygone.cc
# include <iostream>
# include <fstream>
# include "polygone.h"
Polygone::Polygone(string nom)
{
std::ifstream fichier (nom, ios::in);
std::string line;
if (fichier.is_open())
{
while ( fichier.good() )
{
getline (fichier, line);
std::cout << line << std::endl;
}
}
else
{
std::cerr << "Erreur a l'ouverture du fichier" << std::endl;
}
}
//ifstream fich1 (argv[1], ios::in);
My guess is that the compiler is not recognising Polygone::Polygone(string nom)
as a constructor, but, if this actually is the case, I have no idea why.
Any help?
This question is related to
c++
class
constructor
You are missing the std namespace reference in the cc file. You should also call nom.c_str()
because there is no implicit conversion from std::string
to const char *
expected by ifstream
's constructor.
Polygone::Polygone(std::string nom) {
std::ifstream fichier (nom.c_str(), std::ifstream::in);
// ...
}
This is not only a 'newbie' scenario. I just ran across this compiler message (GCC 5.4) when refactoring a class to remove some constructor parameters. I forgot to update both the declaration and definition, and the compiler spit out this unintuitive error.
The bottom line seems to be this: If the compiler can't match the definition's signature to the declaration's signature it thinks the definition is not a constructor and then doesn't know how to parse the code and displays this error. Which is also what happened for the OP: std::string
is not the same type as string
so the declaration's signature differed from the definition's and this message was spit out.
As a side note, it would be nice if the compiler looked for almost-matching constructor signatures and upon finding one suggested that the parameters didn't match rather than giving this message.
Source: Stackoverflow.com