OpenGL function in a class - c++

Question

I'm creating an OpenGL project which includes ParticleFactory class to generate particles in a scene.
To achieve that I have created a class:
#ifndef PARTICLE_H
#define PARTICLE_H
#include <glad/glad.h>
#include <GLFW/glfw3.h>
#include <glm/glm.hpp>
#include <glm/gtc/matrix_transform.hpp>
#include <glm/gtc/type_ptr.hpp>
#include <iostream>
#include <vector>
#include "vertex.h"
#include <shader_s.h>
class ParticleFactory {
public:
Shader* shader;
std::vector<Particle> particles;
unsigned int VAO, VBO, EBO;
unsigned int nr_particles;
ParticleFactory(unsigned int nr_particles, unsigned int color){
Shader sh("shaders/particle.vs", "shaders/particle.fs");
shader = &sh;
this->nr_particles = nr_particles;
for(unsigned int i = 0; i < nr_particles; i++) {
float x = (rand()%200)/100.0 - 1;
float y = (rand()%200)/100.0 - 1;
float z = (rand()%200)/100.0 - 1;
particles.push_back(Particle(glm::vec4(x, y, z, 0.0)));
}
glGenVertexArrays(1, &VAO);
glGenBuffers(1, &VBO);
glGenBuffers(1, &EBO);
glBindVertexArray(VAO);
glBindBuffer(GL_ARRAY_BUFFER, VBO);
glBufferData(GL_ARRAY_BUFFER, sizeof(base_particle), base_particle, GL_STREAM_DRAW);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, EBO);
glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(base_particle_indices), base_particle_indices, GL_STREAM_DRAW);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, (void*)0);
glEnableVertexAttribArray(0);
}
void draw() {
shader->use();
shader->setMat4("model", model);
shader->setMat4("view", view);
shader->setMat4("projection", projection);
shader->setMat4("transform", transform);
for (int i=0; i<nr_particles; i++) {
shader->setVec4("offset", particles[i].offset);
glBindVertexArray(VAO);
glDrawElements(GL_TRIANGLES, 24, GL_UNSIGNED_INT, 0);
particles[i].offset += glm::vec4(0.0f, -0.001f, 0.0f, 0.0f);
if (particles[i].offset.y <= -1.0f) {
particles[i].offset.y = 1.0f;
}
}
}
};
#endif
My approach here is to first instantiate an object and then call .draw() on the main loop but it doesn't seems to work and I don't know why.

Answer 1

Before we even get to the OpenGL part, you're creating a LOCAL object (sh) and then assigning the address of that to the shader member. At the end of the constructor, sh will be deleted, and thus the shader member will be pointing to … ? First, you'll need to use new/delete (or better yet, use std::unique_ptr< Shader >) to make sure that object is still around when you want to use it.
Try that FIRST!