Class does not cout from constructor?

[jesirose]

I am a complete newbie to C++ (I primarily work in Java & PHP).

I expect this code to print Making a new: Alien when I run it.
It compiles fine, and runs, but it just prints Making a new:
No Alien :(

#include <iostream>
using namespace std;
 
class Alien{
    public:
        string name;
        Alien(){
            cout << "Alien";
        };
};
 
int main(){
    cout << "Making a new: ";
    Alien al();
    return 0;
}

[Banfa]

#include <iostream>
using namespace std;
 
class Alien{
    public:
        string name;
        Alien(){
            cout << "Alien";
        };
};
 
int main(){
    cout << "Making a new: ";
    Alien al();
    return 0;
}

You error is on this line

    Alien al();

this is interpreted as a function prototype, that is you have declared a function that takes no parameters and returns type Alien. This links because the function is not actually called so it does not have to exist.

To instantiate an alien using the default constructor you should change this to

    Alien al;

Additionally you never output an end of line or flush stdout. Output is buffered and the data written to stdout is only guarenteed to be written when expicitly flushed or an end of line character is see.

[diSangro]

I think you should use somethin like

al.Alien();

in your main()

I tried to run the following code with Dev-C++ and it works:

 #include <iostream>
#include <conio.h>
using namespace std;
 
class Alien{
 
    public:
        string name;
        void Alien_view(void){
            cout << "Alien";
        };
};
 
int main(){
    cout << "Making a new: ";
    Alien al;
    al.Alien_view();
    getch();
    return 0;
}

Depending on your compiler you may be not allowed to avoid returned and parameter data type in class method declaration.

diSangro

I am a complete newbie to C++ (I primarily work in Java & PHP).

I expect this code to print Making a new: Alien when I run it.
It compiles fine, and runs, but it just prints Making a new:
No Alien :(

#include <iostream>
using namespace std;
 
class Alien{
    public:
        string name;
        Alien(){
            cout << "Alien";
        };
};
 
int main(){
    cout << "Making a new: ";
    Alien al();
    return 0;
}