Error: Invalid use of non-static data member, variable was not declared in this scope

Question

以下是跳过列表的模板化 class 中的内部嵌套 class。我收到错误："height was not declared in this scope" 在声明 *next.

的行

        class Node{
            public:
                Node(int height){
                    this->height = height;
                }
                Node(Key_t key, Mapped_t obj, int height){
                    value = std::make_pair(key, obj);
                    this->height = height;
                }
                SkipList<Key_t, Mapped_t>::Node *next[height];
                int getHeight(){return height;}
                Key_t getKey(){return value.first;}
                Mapped_t getObj(){return value.second;}
            private:
                std::pair<Key_t, Mapped_t> value;
                int height;
        };

将 value 和 height 的声明移到其他所有内容之前，如下所示，将错误更改为“无效使用非静态数据成员。

         class Node{
                private:
                    std::pair<Key_t, Mapped_t> value;
                    int height;
                public:
                    Node(int height){
                        this->height = height;
                    }
                    Node(Key_t key, Mapped_t obj, int height){
                        value = std::make_pair(key, obj);
                        this->height = height;
                    }
                    SkipList<Key_t, Mapped_t>::Node *next[height];
                    int getHeight(){return height;}
                    Key_t getKey(){return value.first;}
                    Mapped_t getObj(){return value.second;}
            };

我不知道该怎么做才能解决这个问题。这是整个 class:

template <class Key_t, class Mapped_t>
class SkipList{
public:
    SkipList(int prob, int max){
        probOutOf100 = prob;
        maxHeight = max;
        head = new SkipList<Key_t, Mapped_t>::Node(maxHeight);
        tail = new SkipList<Key_t, Mapped_t>::Node(maxHeight);
        for(int i = 0; i < maxHeight; i++){
            head->next[i] = tail;
        }
    }
    ~SkipList(){
        delete head;
        delete tail;
    }

    class Node{
        public:
            Node(int height){
                this->height = height;
            }
            Node(Key_t key, Mapped_t obj, int height){
                value = std::make_pair(key, obj);
                this->height = height;
            }
            SkipList<Key_t, Mapped_t>::Node *next[height];
            int getHeight(){return height;}
            Key_t getKey(){return value.first;}
            Mapped_t getObj(){return value.second;}
        private:
            std::pair<Key_t, Mapped_t> value;
            int height;
    };

    Node *head;
    Node *tail;
    int probOutOf100;
    int maxHeight;
}

Answer 1

问题 1

你不能使用编译器还没有看到的东西，所以把声明移到用法上面解决了这个问题。你已经这样做了。干得好。

问题 2

height只有在构造对象后才能知道。如果对象的大小未知，则无法构造对象，并且 height 决定 next 的大小，这有助于对象的大小。赶上 22.

建议使用 std::vector 代替数组，并在构造函数的 Member Initializer List 中使用 height 初始化向量。示例：

std::vector<SkipList<Key_t, Mapped_t>::Node *> next;

Node(int height): height(height), next(height)
{
}
Node(Key_t key, Mapped_t obj, int height): 
    value(std::make_pair(key, obj)),
    height(height), 
    next(height)
{
}

Answer 2

在下面一行

SkipList<Key_t, Mapped_t>::Node *next[height];

您正试图声明一个指针数组。但是，您不能这样做，除非 height 在编译时已知。

您可能希望将其更改为 vector 并在运行时初始化它。

std::vector<SkipList<Key_t, Mapped_t>::Node*> next;


...

Node(int height) : next(height) {
    this->height = height;
}

PS 我不确定什么数据结构使用指针数组作为节点的 "next" 节点。只是想一想。

Error: Invalid use of non-static data member, variable was not declared in this scope

Error: Invalid use of non-static data member, variable was not declared in this scope

c++

inner-classes

问题 1

问题 2