C++ - 从类内部包含 typedef 结构

Question

My question is about the inclusion of a typedef struct (or at least I think it is). It's probably silly but I couldn't figure out what's wrong with my code.

I have a Node.h header that declares a class Node :

class Node {
public:
    Node(/*some parameters*/); // Class constructor

    typedef struct{ // This represents a weighted edge of weight "weight" from the current node to another node "node"
        Node* node;
        double weight;
    }EdgeInfo;

    vector<EdgeInfo*> OutEdges; // This vector represents the outgoing weighted edges from this node
};

So I figured out that's the only place in my code I can declare the struct because that's the only place where I can declare EdgeInfo that "knows" what a Node class object is.

Then I have a Graph.h header, including the Node.h file, that declares a Graph class.

Now in the Graph.cpp file I'm implementing a function that loops on all the outgoing edges of a Node , more or less like this:

Node* current = /*passing an object of class Node*/

for(EdgeInfo* out : current->OutEdges){           
    /*working on the edges*/
}

The problem is that when I compile I get the error error: 'EdgeInfo' was not declared in this scope at the for loop.

As you probably can see I'm kind of a C++ newbie. I thought that by including Node.h I could use the ´typedef struct` definitions inside the class the same way I use variables and functions. Am I wrong? Or didn't I understand how includes work in C++?

I hope I didn't miss any detail. Thank you so much for the help!

Answer 1

" So I figured out that's the only place in my code I can declare the struct because that's the only place where I can declare EdgeInfo that "knows" what a Node class object is. "

You could use a forward declaration . A another link: forward declaration, stackoverflow .

class Node; // forward declaration

struct EdgeInfo
{ 
    Node* node; // now, `EdgeInfo` knows that a class named `Node` is defined somewhere.
    double weight;
};

class Node {
public:
    Node(/*some parameters*/); // Class constructor

    vector<EdgeInfo*> OutEdges; // This vector represents the outgoing weighted edges from this node
};

Now when you include node.h in graph.cpp , or Graph.h , it'll be aware about EdgeInfo .