Question

I’m new to C++/CLI and I’m wondering what is “best practice” regarding managed type data members. Declaring as handle:

public ref class A {
public:
    A() : myList(gcnew List<int>()) {}
private:
    List<int>^ myList;
};

or as a value:

public ref class B {
private:
    List<int> myList;
};

Can’t seem to find definitive advice on this.

Answer 1

When writing managed C++ code, I’m in favor of following the conventions used by the other managed languages. Therefore, I’d go with handles for class-level data members, and only use values (stack semantics) where you’d use a using statement in C#.

If your class member is a value, then replacing the object entirely means that the object would need a copy constructor defined, and not many .NET classes do. Also, if you want to pass the object to another method, you’ll need to use the % operator to convert from List<int> to List<int>^. (Not a big deal to type %, but easy to forget, and the compiler error just says it can’t convert List<int> to List<int>^.)

//Example of the `%` operator
void CSharpMethodThatDoesSomethingWithAList(List<int>^ list) { }

List<int> valueList;
CSharpMethodThatDoesSomethingWithAList(%valueList);

List<int>^ handleList = gcnew List<int>();
CSharpMethodThatDoesSomethingWithAList(handleList);