c++ - 使用未声明的标识符 C++

Question

我最近一直在学习 C++，我一直在尝试创建一个简单的类拆分为一个头文件和一个源文件。但是，我似乎不断收到此错误:

ship.cpp:21:9: error: use of undeclared identifier 'image'
        return image;
               ^
1 error generated.

我在下面包含了源代码:

ma​​in.cpp:

#include <iostream>

#include <allegro5/allegro.h>
#include <allegro5/allegro_image.h>
#include <allegro5/allegro_native_dialog.h>

#include <ship.h>

int main(int argc, char **argv){
    ALLEGRO_DISPLAY *display = nullptr;
    ALLEGRO_BITMAP *image = nullptr;


    if(!al_init()){
        al_show_native_message_box(display, "Error", "Error", "Failed to initialise allegro", NULL, ALLEGRO_MESSAGEBOX_ERROR);
        return 0;
    }

    if(!al_init_image_addon()) {
        al_show_native_message_box(display, "Error", "Error", "Failed to initialize al_init_image_addon!", NULL, ALLEGRO_MESSAGEBOX_ERROR);
        return 0;
    }

    display = al_create_display(800,600);
      if(!display) {
        al_show_native_message_box(display, "Error", "Error", "Failed to initialize display!", NULL, ALLEGRO_MESSAGEBOX_ERROR);
        return 0;
      }


    Ship ship("image.jpg");
    al_draw_bitmap(ship.get_image(), 200, 200, 0);

    al_flip_display();
    al_rest(2);
    return 0;
}

ship.h:

#ifndef SHIP_H
#define SHIP_H
#include <iostream>
#include <allegro5/allegro.h>
#include <allegro5/allegro_image.h>

class Ship
{
    ALLEGRO_BITMAP *image;

    private:
        int width;
        int height;

    public:
        Ship(std::string image_file);
        ALLEGRO_BITMAP *get_image();
};

#endif

ship.cpp:

#include <allegro5/allegro.h>
#include <allegro5/allegro_image.h>
#include <allegro5/allegro_native_dialog.h>
#include <iostream>

#include <ship.h>




Ship::Ship(std::string image_file){
    image = al_load_bitmap(image_file.c_str());
    if(image == nullptr){
        std::cout << "Ship went down." << std::endl;
    }
    std::cout << "Ship loaded successfully." << std::endl;
}   


ALLEGRO_BITMAP *get_image(){
    return image;
}

Answer 1

您错误地定义了函数。 get_image() 是 Ship 类的成员。您的定义创建了一个独立的函数。

ALLEGRO_BITMAP *get_image(){

应该是:

ALLEGRO_BITMAP* Ship::get_image(){

(星号重新定位以提高可读性)