C2039: Class is not a member of Namespace - c++

Question

Mage/Interface/Context.h
#pragma once
#include <Mage/Interface/Element.h>
#include <Mage/Renderer/RenderingContext.h>
#include <Mage/Renderer/VertexBuffer.h>
#include <glm/glm.hpp>
namespace Mage {
namespace Interface {
class Context {
protected:
RenderingContext* ctx;
VertexBuffer* vbo;
glm::mat4 projection;
Mage::Interface::Frame* uiParent;
public:
Context(RenderingContext* ctx);
~Context();
void render();
Mage::Interface::Frame* createFrame();
};
}
}
Mage/Interface/Element.h
#pragma once
#include <vector>
#include <Mage/Interface/Context.h>
#include <glm/glm.hpp>
namespace Mage {
namespace Interface {
class Element {
protected:
Mage::Interface::Context* ctx;
std::vector<Element*> children;
glm::vec3 position;
float scale;
public:
virtual void draw();
void attach(Element* child) {
this->children.push_back(child);
}
inline glm::vec3 getPosition() {
return this->position;
}
float getScale() {
return this->scale;
}
};
// Frame is an untextured, single colour quad. Frame may contain other
// Elements.
class Frame : public Element {
public:
Frame();
Frame(glm::vec3 pos);
Frame(float width, float height);
Frame(glm::vec3 pos, float width, float height);
};
}
}
This gives me the following errors:
Error C2039 'Context': is not a member of 'Mage::Interface' Mage2D c:\users\jesse\documents\visual studio 2015\projects\mage2d\include\mage\interface\element.h 14
Error C2238 unexpected token(s) preceding ';' Mage2D c:\users\jesse\documents\visual studio 2015\projects\mage2d\include\mage\interface\element.h 14
Error C2143 syntax error: missing ';' before '*' Mage2D c:\users\jesse\documents\visual studio 2015\projects\mage2d\include\mage\interface\element.h 14
Error C4430 missing type specifier - int assumed. Note: C++ does not support default-int Mage2D c:\users\jesse\documents\visual studio 2015\projects\mage2d\include\mage\interface\element.h 14
When I take out Mage::Interface::Context* ctx, the code compiles fine. I figured I must have missed a semi colon, but I can't see it - it all seems to check out just fine to me.

Answer 1

You have a circular dependency. Element.h includes Context.h and Context.h includes Element.h, that's not going to work.
The way to solve that is to forward-declare types instead of including their headers whenever you can, it'll also reduce compile times.