How to: Iterate Over a Generic Collection with for each

The Generics (C++ Component Extensions) feature of Visual C++ allows you to create generic collections.

Example

This sample shows how to use for each with a simple generic value type collection.

// for_each_generics.cpp
// compile with: /clr
using namespace System;
using namespace System::Collections::Generic;

generic <class T>
public value 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;
      }

      virtual property T Current {
         T get() {
            return colInst->data[currentIndex];
         }
      };

      property Object^ CurrentNonGeneric {
         virtual Object^ get() = System::Collections::IEnumerator::Current::get {
            return colInst->data[currentIndex];
         }
      };

      virtual void Reset() {}
      ~enumerator() {}

      MyArray^ colInst;
      int currentIndex;
   };

   array<T>^ data;

   virtual IEnumerator<T>^ GetEnumerator() {
      return gcnew enumerator(*this);
   }
   virtual System::Collections::IEnumerator^ GetEnumeratorNonGeneric() = System::Collections::IEnumerable::GetEnumerator {
      return gcnew enumerator(*this);
   }
};

int main() {
   MyArray<int> col = MyArray<int>( gcnew array<int>{10, 20, 30 } );

   for each ( Object^ c in col )
      Console::WriteLine((int)c);
}

10
20
30

See Also

Reference

for each, in