current()

template<typename type_t >

virtual const type_t & xtd::collections::generic::ienumerator< type_t >::current ( ) const

pure virtual

Gets the element in the collection at the current position of the enumerator.

Returns

The element in the collection at the current position of the enumerator.

Examples

The following code example demonstrates the implementation of the IEnumerator interfaces for a custom collection. In this example, xtd::collections::generic::ienumerator::move_next is not explicitly called, but it is implemented to support the use of foreach (for each in Visual Basic). This code example is part of a larger example for the IEnumerator interface.

// When you implement ienumerable, you must also implement ienumerator.
class people_enum : public ienumerator<person> {
private:
  // Enumerators are positioned before the first element
  // until the first move_next() call.
  size position_ = box_integer<size>::max_value;
 
public:
  const list<person>& people;
 
  explicit people_enum(const list<person>& people) : people {people} {}
 
  bool move_next() override {
    ++position_;
    return position < people.count();
  }
 
  void reset() override {position_ = box_integer<size>::max_value;}
 
  const person& current() const override {
    try {
      return people[position_];
    } catch (const index_out_of_range_exception& e) {
      throw invalid_operation_exception {csf_};
    }
  }
};

Remarks

xtd::collections::generic::ienumerator::current is undefined under any of the following conditions:

• The enumerator is positioned before the first element in the collection, immediately after the enumerator is created. xtd::collections::generic::ienumerator::move_next must be called to advance the enumerator to the first element of the collection before reading the value of xtd::collections::generic::ienumerator::current.
• The last call to xtd::collections::generic::ienumerator::move_next returned false, which indicates the end of the collection.
• The enumerator is invalidated due to changes made in the collection, such as adding, modifying, or deleting elements.

xtd::collections::generic::ienumerator::current returns the same object until xtd::collections::generic::ienumerator::move_next is called. xtd::collections::generic::ienumerator::move_next sets xtd::collections::generic::ienumerator::current to the next element.

Notes to Implementers

Implementing this interface requires implementing the nongeneric IEnumerator interface. The xtd::collections::generic::ienumerator::current property appears on both interfaces, and has different return types. Implement the nongeneric xtd::collections::generic::ienumerator::current property as an explicit interface implementation. This allows any consumer of the nongeneric interface to consume the generic interface.

Implemented in xtd::collections::generic::enumerator< type_t >.