Mixed management in C++

Question

I have added a class to my program and tested it. I was really surprised that there was any real errors. Here is the code:

#pragma once
#include "Iingredient.h"
#include <string>
#include <vector>

using namespace std;

ref class Recipe{
private:
    string partsName;
    vector<Iingredient> ing;
public:
    Recipe(){}

};

And here are the errors:

Error 23 error C4368: cannot define 'partsName' as a member of managed 'Recipe': mixed types are not supported c:\users\user\documents\visual studio 2010\projects\smestras2_l1\Recipe.h 10 1 file2_L1

Error 24 error C4368: cannot define 'ing' as a member of managed 'Recipe': mixed types are not supported c:\users\user\documents\visual studio 2010\projects\smestras2_l1\Recipe.h 11 1 file2_L1

I googled a bit and found out that its about managed and unmanaged code. How to fix this? Is it related with manged and unmanaged code or not? if so how?

Answer 1

I agree with others: you shouldn't use C++/CLI in most circumstances, you should use C# (or another "normal" managed language) for that (assuming you want to write a .Net application). C++/CLI is useful mostly in special circumstances, like interoperating between managed and unmanaged code.

If you're sure you want use C++/CLI, you can't put native classes into managed ones. But you can put pointers to native classes there:

ref class Recipe{
private:
    string* partsName;
    vector<Iingredient>* ing;
};

The code above works. But you have to keep in mind that those are normal native C++ pointers and that means you have to manually delete them. To do that property, you should read about how destructors and finalizers work in C++/CLI.

Answer 2

When defining ref class Recipe, you made it managed. But std::string and std::vector are umanaged types. You are trying to declare native variables in managed class, but it is not allowed.

Seems, you are novice in C++. Just, don't use C++/CLI. Consider C#, if you target .Net or unmanaged C++.