将class作为函数参数传递时C ++不完整类型错误

Question

I'm trying to use the following code, in a header file, to define a class and a function which takes a vector of pointers to this class as a parameter. However, on compilation I get an incomplete type error.

    #ifndef OBJECTS_H
    #define OBJECTS_H

    #include <glm/glm.hpp>
    #include <vector>

    struct Shape {
        glm::vec3 emission;
        float shininess;
        glm::vec3 Ka;
        glm::vec3 Ks;
        glm::vec3 Kd;

        Shape(glm::vec3 emission, float shininess, glm::vec3 Ka, glm::vec3 Ks, glm::vec3 Kd);
        float intersects(const glm::vec4 start, const glm::vec4 direction);
        virtual glm::vec4 randomPoint();
        virtual glm::vec4 getNormal(const glm::vec4 &p);
        virtual bool isLight();
    };

    void LoadModel(vector<Shape *> &scene, const char *path);

    #endif

Giving the error:

error: incomplete type is not allowed
      void LoadModel(vector<Shape *> &scene, const char *path);

Why is this error occurring, and what is the correct way to write this code?

Answer 1

Change your function declaration to properly scope the std::vector

void LoadModel(std::vector<Shape *> &scene, const char *path);

If that doesn't fix it, then the error is about Shape . You need to make sure that at the definition of function LoadModel the compiler has the complete definition of class Shape if that function requires access to any of its data members.

Answer 2

Vectors, like all other standard library containers, are in the std namespace. Therefore, you should refer to it as std::vector since you don't have the line using namespace std; .

Answer 3

When I encounter these seemingly obscure errors, I try to remove the complexity in a few additional versions of the code.

In this case, I'd create a few additional function declarations right ahead of the one with the problem:

LoadShape(Shape, const char*); LoadShape(vector<char>, const char*);

That would show the same error for the vector<char> param, providing a clue... Obviously char wouldn't be an incomplete type so the issue is with vector and, in general, my errors in using STL types are related to either namespace issues or template-related voodoo.