How to call to C++ code from C++/CLI code?

Question

I have created a C++/CLI (Visual C++) project in visual studio 2010 professional. I then added a very small C++ class to the project. Followng is the code

#include <stdafx.h>
#include <iostream>

using namespace std;

    class Tester
    {

    public:
        Tester(){};

        void show()
        {
            cout << "OKOK..Printing" << endl;
        }

    };

Now, I dragged and dropped a button to the automatically built GUI form, and I am about to call the above code from the button. Following is the code of the button.

private: System::Void button1_Click(System::Object^  sender, System::EventArgs^  e) {
                 Tester ^t = gcnew Tester();
                             //Test t; - giving errors as well

             }
    };

When I execute the code, I get the following error

1>------ Build started: Project: testdamn, Configuration: Debug Win32 ------
1>Build started 7/1/2013 12:59:38 PM.
1>InitializeBuildStatus:
1>  Touching "Debug\testdamn.unsuccessfulbuild".
1>GenerateTargetFrameworkMonikerAttribute:
1>Skipping target "GenerateTargetFrameworkMonikerAttribute" because all output files are up-to-date with respect to the input files.
1>ClCompile:
1>  All outputs are up-to-date.
1>  Test.cpp
1>  testdamn.cpp
1>c:\users\yohan\documents\visual studio 2010\projects\testdamn\testdamn\Form1.h(79): error C2065: 'Tester' : undeclared identifier
1>c:\users\yohan\documents\visual studio 2010\projects\testdamn\testdamn\Form1.h(79): error C2065: 't' : undeclared identifier
1>c:\users\yohan\documents\visual studio 2010\projects\testdamn\testdamn\Form1.h(79): error C2061: syntax error : identifier 'Tester'
1>  Generating Code...
1>
1>Build FAILED.
1>
1>Time Elapsed 00:00:01.86
========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========

I also noticed when I removed the class call from the button, the program build fine. So, how can I call to these C++ classes from C++/CLI ?

Did you #include the Tester class's header file into the GUI form? — Marcelo Cantos
– Marcelo Cantos, Commented Jul 1, 2013 at 7:31
@MarceloCantos: No, because this do not have a header file. Is that is required? — PeakGen
– PeakGen, Commented Jul 1, 2013 at 7:34
Yes. The GUI code needs to see the definition of the Tester class. That's why it's complaining: 'Tester' : undeclared identifier. Also, you can't treat it like a .Net class. ^t and gcnew won't work. — Marcelo Cantos
– Marcelo Cantos, Commented Jul 1, 2013 at 7:35
@MarceloCantos: Great! Thank you a lot! I really to have help from all of you until I finish my final project :) — PeakGen
– PeakGen, Commented Jul 1, 2013 at 7:47

Cody Gray · Accepted Answer · 2013-07-01 07:35:50Z

5

Look at the compiler errors you're receiving:

1>c:\...\testdamn\Form1.h(79): error C2065: 'Tester' : undeclared identifier
1>c:\...\testdamn\Form1.h(79): error C2065: 't' : undeclared identifier
1>c:\...\testdamn\Form1.h(79): error C2061: syntax error : identifier 'Tester'

The compiler is telling you that it cannot find any class named Tester and therefore cannot use it.

In order to use your Tester class, you need to include the header file that contains its definition in the file that contains your Form class's definition. This is the same as how you had to include the iostream header in order to use std::cout.

But once you fix this, you'll have another problem: you're trying to use gcnew to instantiate Tester, which is an unmanaged class. gcnew is intended to instantiate managed classes, and allocates memory from the managed heap. You want to use the regular C++ new operator to instantiate regular C++ unmanaged classes. Once the compiler is able to see the definition of the Tester class, it will notice this mismatch and generate another error.

answered Jul 1, 2013 at 7:35

Cody Gray♦

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1 Comment

PeakGen Over a year ago

Great! Thank you a lot! I really wish I can get help from all of you until I finish my final project :) I am marking this as the answer. Thanks for guiding me to address the next possible error as well!

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