Vector of Custom Objects - c++

Question

I am trying to create a vector of custom objects defined in a header file and then initialize them in the actual cpp file. I'm getting the following errors in Visual Studio:
error C2976: 'std::vector' : too few template arguments
error C2065: 'Particle' : undeclared identifier
error C2059: syntax error : '>'
In the code below, the vector is defined in Explosion.h.
Particle.h:
#pragma once
class Particle : public sf::CircleShape {
public:
float speed;
bool alive;
float vx;
float vy;
Particle(float x, float y, float vx, float vy, sf::Color color);
~Particle();
};
Particle.cpp:
#include <SFML/Graphics.hpp>
#include "Particle.h"
Particle::Particle(float x, float y, float vx, float vy, sf::Color color) {
// Inherited
this->setPosition(x, y);
this->setRadius(5);
this->setFillColor(color);
// Player Defined Variables
this->speed = (float).05;
this->alive = true;
this->vx = vx;
this->vy = vy;
}
Particle::~Particle() {
}
Explosion.h:
static const int NUM_PARTICLES = 6;
#pragma once
class Explosion {
public:
std::vector<Particle*> particles;
bool alive;
Explosion();
~Explosion();
};
Explosion.cpp:
#include <SFML/Graphics.hpp>
#include "Particle.h"
#include "Explosion.h"
Explosion::Explosion() {
this->alive = true;
// Add Particles to vector
for (int i = 0; i < NUM_PARTICLES; i++) {
this->particles.push_back(new Particle(0, 0, 0, 0, sf::Color::Red));
}
}
Explosion::~Explosion() {
}
I'm sure there is something fundamentally wrong here since C++ is fairly new to me.

Answer 1

You need to tell Explosion.h what a Particle is.
In this case, Explosion.h is using Particle*, so a forward declartion will suffice.
Explosion.h
class Particle; // forward declaration of Particle
class Explosion {
// ...
};
You could also simply #include "Particle.h, however as your projects increase using forward declarations (instead of direct includes) can significantly reduce your build times.