Function Pointers in C++/CX

Question

Background

I'm writing a Windows Store App in C++ using the Windows Store Unit Test Project. While trying to figure out how to test that an exception was raised, I found Assert::ExpectedException in CppUnitTestAssert.h. Its signatures are below:

template<typename _EXPECTEDEXCEPTION, typename _RETURNTYPE> static void ExpectException(_RETURNTYPE (*func)(), const wchar_t* message = NULL, const __LineInfo* pLineInfo = NULL)
{
    ...
}

and

template<typename _EXPECTEDEXCEPTION, typename _FUNCTOR> static void ExpectException(_FUNCTOR functor, const wchar_t* message = NULL, const __LineInfo* pLineInfo = NULL)` 
{
    ...
}

The Question Is:

It's been a LONG time since I coded in C++, so I'm having difficulty figuring out how to call the method correctly. I keep getting the following error:

'Microsoft::VisualStudio::CppUnitTestFramework::Assert::ExpectException' : none of the 2 overloads could convert all the argument types

I realize this may be actually be a misunderstanding of "pure" C++, but I'm not sure if C++/CX may have different rules for using function pointers that C++. Or at least what I remember the rules to be.

EDIT:

I'm attempting to use the function pointer overload, _RETURNTYPE (*func)(), not the __FUNCTOR overload. Here is the code that is failing to compile.

Assert::ExpectException<InvalidArgumentException, int>(&TestClass::TestMethod);

Here is TestMethod:

void TestMethod()
{
}

Unrequited

...What are you trying to pass as a _FUNCTOR? – Nell

Yeah, that would probably have helped, wouldn't it? – Unrequited

I think you might be better off trying the _FUNCTOR version. It seems to me that the first overload would match a global function, not a member function as you're trying to use... or just try using a global function to test). – Eulau

I could certainly try that. – Unrequited

Answer 1

The second type in the ExpectException template (_RETURNTYPE in the declaration), needs to match the return type of the function passed into it. You've used int but your function returns void, so this gives a compiler error. If you want to be explicit here the second type should be void. However, as the compiler can figure out the type from the function parameter you don't need to specify it. Try this:

Assert::ExpectException<InvalidArgumentException>(TestClass::TestMethod);

Redolent