gistfile1.hpp

template <typename Callable, typename ResultPtr>
class nsRunnableFunctor
  : public nsARunnableFunctor
{
  Callable mCallable;
  ResultPtr mResultPtr;

public:

  nsRunnableFunctor(Callable callable, ResultPtr resultPtr)
    : mCallable(callable)
    , mResultPtr(resultPtr)
  {}

  nsresult Run()
  {
    // This line enforces everything that matters about ResultPtr and Callable:
    // that mResultPtr can be dereferenced, that mCallable is callable with no
    // arguments, that the result of this call is non-void, and that the
    // result can be copied into the L-value resulting from the expression
    // *mResultPtr.  No other properties of the template parameters are in any
    // way constrained, not even implicitly.  Do I feel clever?  Yes, I do.
    *mResultPtr = mCallable();
    return AfterRun();
  }

};