在另一个结构中声明一个结构

Question

in my header file:

private:
struct movieNode {
    string title;

    castNode *castHead;

    movieNode *prev;
    movieNode *next;
};

struct castNode {
    string name;

    castNode *next;

};

movieNode *head;
movieNode *last;

but the compiler error is:

expected ';' before '*' token

my aim is that every movieNode should have a title and a cast list (with castNode). thanks in advance.

Answer 1

movieNode needs to at least be able to see an incomplete type called castNode . At the moment, the compiler is going "Huh, castNode ? What the hell is that?" because it hasn't seen the definition of castNode yet. You can avoid it in this case by simply defining castNode before you define movieNode . Just swap the two structs around.

In other cases, where you have a cyclic dependency (if castNode had a pointer to a movieNode too, for example), you can use a forward declaration to provide an incomplete type (it would look like class castNode; ) and then define it properly later.

Answer 2

private:
     struct castNode; // <- add this
     struct movieNode
     {
             string     title;
             castNode*  castHead;
             movieNode* prev;
             movieNode* next;
     };
     struct castNode
     {
             string    name;
             castNode* next;
     };
     movieNode*   head;
     movieNode*   last;

Answer 3

Declare castNode before movienode .

Only then movienode "knows" what a castNode is.