重载迭代器类的增量运算符

Question

我一直试图重载++运算符，以在列表中移动迭代器，但我一直收到错误C2460"list:：iterator:：++"：使用"list：：iterator"

template <typename E>
class List : public SLinkedList<E> {
public:
// NOTE THE DIFFERENT LETTER – IT IS ONLY USED HERE! 
// Use E everywhere else! m
// For a nested class, methods are declared and defined *INSIDE*
// the class declaration.
template <typename I>
class Iterator {
public:
    // Give List access to Iterator private fields.
    friend class List<E>;
    // These are the minimum methods needed.
    E operator* {nodePosition->elem}; //dereference the iterator and return a value
    Iterator<E> operator++ {nodePosition = nodePosition->next};  //increment the iterator
    Iterator<E> operator-- {
        nodePosition = nodePosition->prev;
    }  //decrement the iterator
    bool operator==(const Iterator<E> p)  { 
        return (nodePosition == p)
    }  //test equality of iterators
    bool operator!=(const Iterator<E> p) {
        return (nodePosition != p)
    }   //test inequality of iterators

private:
    // Constructors & destructor here since only want List class to access.
    // List constructor called from List::begin(). Use initializer list or
    // create class copy constructor and assignment overload.
    Iterator(const List<E>* sl) : llist(sl) {
        nodePosition = sl->head;
    }
    // Class fields.
    const List<E>* llist;     //give Iterator class a handle to the list
    Node<E>* nodePosition;  //abstracted position is a pointer to a node
}; /** end Iterator class **/
   /* The Iterator class is now fully defined. The rest of these
   statements must go AFTER the Iterator class or the compiler
   won’t have complete information about their data types.
   */
   // REQUIRED: While not necessary for the code to work, my test suite needs
   // this defined. Create a less cumbersome name for Iterator<E>. Use 
   // anywhere you would have used List<E>::Iterator<E> in class List. Allows 
   // this syntax in main() -- List<int>::iterator instead of List<int>::Iterator<int>.
typedef typename List<E>::Iterator<E> iterator;
/***    All method declarations and fields for the List class go here.
Any method that returns an iterator must be defined here.
***/
iterator begin() const {  //return an iterator of beginning of list
                          // Call iterator constructor with pointer to List that begin() was 
                          // called with.
    return iterator(this);
}
E back();
E pop_back();
void push_back(const E e);

}；/**end List类声明**/

Answer 1

以下方法定义格式错误：

E operator* {nodePosition->elem}; //dereference the iterator and return a value
Iterator<E> operator++ {nodePosition = nodePosition->next};  //increment the iterator
Iterator<E> operator-- {
    nodePosition = nodePosition->prev;
}  //decrement the iterator

尽管这些方法都不需要参数，但仍然需要()。编译器可能将它们视为某种类型的变量定义，并让事情持续足够长的时间，以获得OP正在报告的错误消息。

E operator*() {nodePosition->elem}; //dereference the iterator and return a value
Iterator<E> operator++() {nodePosition = nodePosition->next};  //increment the iterator
Iterator<E> operator--() {
    nodePosition = nodePosition->prev;
}  //decrement the iterator

它们也都是返回值的状态，但没有一个函数体这样做。在这段代码发挥作用之前，还需要做更多的工作。