如何使用构造函数在另一个类中创建一个对象？

Question

所以我正在研究我的代码,它以模块化的方式设计.现在,我的一个班级; 被调用Splash必须创建另一个被调用的类的对象Emitter.通常你只需要创建对象并完成它,但这在这里不起作用,因为Emitter类有一个自定义构造函数.但是当我尝试创建一个对象时,它不起作用.

举个例子;

Emitter有一个像这样的构造函数:Emitter::Emitter(int x, int y, int amount);并且需要创建,以便可以在Splash类中访问它.

我试图这样做,但它不起作用:

class Splash{
    private:
        Emitter ps(100, 200, 400, "firstimage.png", "secondimage.png"); // Try to create object, doesn't work.
    public:
       // Other splash class functions.
}

我也试过这个,但也没用:

class Splash{
    private:
        Emitter ps; // Try to create object, doesn't work.
    public:
       Splash() : ps(100, 200, 400, "firstimage.png", "secondimage.png")
       {};
}

编辑:我知道第二种方式应该可行,但事实并非如此.如果我删除该Emitter部分,代码工作.但是当我第二种方式,没有窗口打开,没有应用程序执行.

那么如何创建我的Emitter对象Splash呢？

编辑:

这是我的发射器类和标头的代码: Header

// Particle engine for the project

#ifndef _PARTICLE_H_
#define _PARTICLE_H_

#include <vector>
#include <string>
#include "SDL/SDL.h"
#include "SDL/SDL_image.h"
#include "image.h"

extern SDL_Surface* gameScreen;

class Particle{
    private: // Particle settings
        int x, y;
        int lifetime;
    private: // Particle surface that shall be applied
        SDL_Surface* particleScreen;
    public: // Constructor and destructor
        Particle(int xA, int yA, string particleSprite);
        ~Particle(){};
    public: // Various functions
        void show();
        bool isDead();
};

class Emitter{
    private: // Emitter settings
        int x, y;
        int xVel, yVel;
    private: // The particles for a dot
        vector<Particle> particles;
        SDL_Surface* emitterScreen;
        string particleImg;
    public: // Constructor and destructor
        Emitter(int amount, int x, int y, string particleImage, string emitterImage);
        ~Emitter();
    public: // Helper functions
        void move();
        void show();
        void showParticles();
};

#endif

这是发射器功能:

#include "particle.h"

// The particle class stuff
Particle::Particle(int xA, int yA, string particleSprite){
    // Draw the particle in a random location about the emitter within 25 pixels    
    x = xA - 5 + (rand() % 25);
    y = yA - 5 + (rand() % 25);
    lifetime = rand() % 6;
    particleScreen = Image::loadImage(particleSprite);
}

void Particle::show(){
    // Apply surface and age particle
    Image::applySurface(x, y, particleScreen, gameScreen);
    ++lifetime;
}

bool Particle::isDead(){
    if(lifetime > 11)
        return true;
    return false;
}

// The emitter class stuff

Emitter::Emitter(int amount, int x, int y, string particleImage, string emitterImage){
    // Seed the time for random emitter
    srand(SDL_GetTicks());
    // Set up the variables and create the particles
    x = y = xVel = yVel = 0;
    particles.resize(amount, Particle(x, y, particleImage));
    emitterScreen = Image::loadImage(emitterImage);
    particleImg = particleImage;
}

Emitter::~Emitter(){
    particles.clear();
}

void Emitter::move(){
}

void Emitter::show(){
    // Show the dot image.
    Image::applySurface(x, y, emitterScreen, gameScreen);
}

void Emitter::showParticles(){
    // Go through all the particles
    for(vector<Particle>::size_type i = 0; i != particles.size(); i++){
        if(particles[i].isDead() == true){
            particles.erase(particles.begin() + i);
            particles.insert(particles.begin() + i, Particle(x, y, particleImg));
        }
    }
    // And show all the particles
    for(vector<Particle>::size_type i = 0; i != particles.size(); i++){
        particles[i].show();
    }
}

这里还有Splash Class和Splash Header.

Answer 1

第二个选项应该工作,我会开始查看编译错误,看看它为什么没有.实际上,请发布与此代码相关的任何编译错误.

在此期间,您可以执行以下操作:

class Splash{
   private:
     Emitter* ps;
   public:
     Splash() { ps = new Emitter(100,200,400); }
     Splash(const Splash& copy_from_me) { //you are now responsible for this }
     Splash & operator= (const Splash & other) { //you are now responsible for this}

     ~Splash() { delete ps; }

};