C ++ / CLI IEnumerable and implementation of IEnumerator

Question

Does anyone have a working, step-by-step example of how to implement IEnumerable and IEnumerator in C ++ / CLI? Also, does anyone know how to fix the following code from MS Connect that does not compile in Visual Studio 2005?

http://connect.microsoft.com/VisualStudio/feedback/details/101089/how-to-implement-ienumerable-t-and-ienumerable-c-cli

using namespace System; using namespace System::Collections::Generic; generic <class T> public ref struct MyArray : public IEnumerable<T> { MyArray( array<T>^ d ) { data = d; } ref struct enumerator : IEnumerator<T> { enumerator( MyArray^ myArr ) { colInst = myArr; currentIndex = -1; } bool MoveNext() { if( currentIndex < colInst->data->Length - 1 ) { currentIndex++; return true; } return false; } property T Current { T get() { return colInst->data[currentIndex]; } }; // This is required as IEnumerator<T> also implements IEnumerator property Object^ Current2 { virtual Object^ get() new sealed = System::Collections::IEnumerator::Current::get { return colInst->data[currentIndex]; } }; void Reset() {} ~enumerator() {} MyArray^ colInst; int currentIndex; }; array<T>^ data; IEnumerator<T>^ GetEnumerator() { return gcnew enumerator(this); } virtual System::Collections::IEnumerator^ GetEnumerator2() new sealed = System::Collections::IEnumerable::GetEnumerator { return gcnew enumerator(this); } }; int main() { int retval = 0; MyArray<int>^ col = gcnew MyArray<int>( gcnew array<int>{10, 20, 30 } ); for each( Object^ c in col ) { retval += (int)c; } retval -= 10 + 20 + 30; Console::WriteLine("Return Code: {0}", retval ); return retval; } 

The compiler cannot find implementations of the enumeration method:

 error C3766: 'MyArray<T>::enumerator' must provide an implementation for the interface method 'bool System::Collections::IEnumerator::MoveNext(void)' c:\Projects\VCNET\2005\IEnumerable\IEnumerable\IEnumerable.cpp 55 error C3766: 'MyArray<T>::enumerator' must provide an implementation for the interface method 'void System::Collections::IEnumerator::Reset(void)' c:\Projects\VCNET\2005\IEnumerable\IEnumerable\IEnumerable.cpp 55 error C3766: 'MyArray<T>::enumerator' must provide an implementation for the interface method 'T System::Collections::Generic::IEnumerator<T>::Current::get(void)' c:\Projects\VCNET\2005\IEnumerable\IEnumerable\IEnumerable.cpp 55 error C3766: 'MyArray<T>' must provide an implementation for the interface method 'System::Collections::Generic::IEnumerator<T> ^System::Collections::Generic::IEnumerable<T>::GetEnumerator(void)' c:\Projects\VCNET\2005\IEnumerable\IEnumerable\IEnumerable.cpp 68 

Answer 1

This compilation for me without a single warning (on VS2010):

 using namespace System; using namespace System::Collections::Generic; generic <class T> public ref struct MyArray : public IEnumerable<T> { MyArray( array<T>^ d ) { data = d; } ref struct enumerator : IEnumerator<T> { enumerator( MyArray^ myArr ) { colInst = myArr; currentIndex = -1; } virtual bool MoveNext() = IEnumerator<T>::MoveNext { if( currentIndex < colInst->data->Length - 1 ) { currentIndex++; return true; } return false; } property T Current { virtual T get() = IEnumerator<T>::Current::get { return colInst->data[currentIndex]; } }; // This is required as IEnumerator<T> also implements IEnumerator property Object^ Current2 { virtual Object^ get() = System::Collections::IEnumerator::Current::get { return colInst->data[currentIndex]; } }; virtual void Reset() = IEnumerator<T>::Reset {} ~enumerator() {} MyArray^ colInst; int currentIndex; }; array<T>^ data; virtual IEnumerator<T>^ GetEnumerator() { return gcnew enumerator(this); } virtual System::Collections::IEnumerator^ GetEnumerator2() = System::Collections::IEnumerable::GetEnumerator { return gcnew enumerator(this); } }; int main() { int retval = 0; MyArray<int>^ col = gcnew MyArray<int>( gcnew array<int>{10, 20, 30 } ); for each( Object^ c in col ) { retval += (int)c; } retval -= 10 + 20 + 30; Console::WriteLine("Return Code: {0}", retval ); return retval; }