在类构造函数中向向量添加值时的变量作用域

Question

我有一个级别类和一个Enemy_control类，该类基于将Enemys作为值的向量。 在我的关卡构造函数中，我有：

Enemy tmp( 1200 );
enemys.Add_enemy( tmp ); // this adds tmp to the vector in Enemy_control

敌人是Enemy_control类型的变量。 这些语句抱怨级别，敌人控制和敌人的某些析构函数问题后，我的程序崩溃。

Level1::Level1() : Levels()
{
bgX1 = -60; // -60
bgX2 = -130; // -110
bgX3 = -240; // -
bgY=0; // is this used anymore?

// characterY=330;
max_right_movement=500;
max_left_movement=300;

 // More test
jump_max = 110;
player_current_y = 340;
jump_spd = 4;
player_current_floor_y = 340;
//CONST_LEVEL1_MAIN_Y = new int( 340 );

scrolling = true;
scrolling_right = true; // this var is in levels

level_alive = true;
restart_level = false;

player_level_x = 300;
player_screen_x = 300;

level_end_point = 1035 * 10;
level_start_point = 0;

// create enemys in the level
Enemy tmp( 1200 );
enemys.Add_enemy( tmp );


//    tmp.Set_enemy( 4600 );
//    enemys.Add_enemy( tmp );
scoreTitle = new MyText(25);
score = new MyText(25);
high_score=0;
//onblock=0;

load( "grafx/level1/clouds.png", "grafx/level1/mountain.png", "grafx/level1/ground.png", "sounds/level1music.ogg" );
}

and enemy.h:

/* Enemy.h
* obg
* 1-13-10
*/

#ifndef ENEMY_H
#define ENEMY_H

#include "Character.h"
#include <vector>

class Enemy : public Character
{
    private:
        int enemy_speed,
            DRAW_X,
            spawn_x,
            distance_to_enemy,
            frame_left,
            frame_right,
            death_frame_x,
            death_frame_y;

        int bullet_fire_rate;

        bool following_player;

    private:
        void Draw_enemy_going_right( SDL_Surface *video_surface );
        void Draw_enemy_going_left( SDL_Surface *video_surface );
        void Draw_death( int bgX3, int y, SDL_Surface *video_surface );

        void Move_frame_left();
        void Move_frame_right();

        void Draw_me( int bgX3, int y, SDL_Surface *video_surface, int player_level_x, int player_screen_x );

        void Fire_bullet();

    public:
        Enemy( int spawn_x );
        ~Enemy();

        //void Set_enemy( int spawn_x );
        void Draw( int bgX3, int y, SDL_Surface *video_surface, int player_level_x, int player_screen_x );
        bool Following_player();

};

class Enemy_control
{
    private:
        vector< Enemy > enemy_vector; // change this to a vector

    public:
        Enemy_control();
        ~Enemy_control();

        void Add_enemy( Enemy a_enemy );
        void Draw( int bgX3, int y, SDL_Surface *video_surface, int player_level_x, int player_screen_x );
        //void Free_list_from_memory();
};

敌人构造函数：

敌人:: Enemy（int spawn_x）：Character（）{

character_image.load（“ grafx / enemy1.gif”）;

health = 400;
damage = 20;

DRAW_X = spawn_x;
this->spawn_x = spawn_x;

distance_to_enemy = 230;
enemy_speed = 3;
frame_left = 0;
frame_right = 0;
death_frame_x = 390;
death_frame_y = 0;

following_player = false;
bullet_fire_rate = 0;

sprite_info.w = 63;
sprite_info.h = 74;
cout << "enemy built please call Set_enemy()\n";

}

有任何想法吗？

Answer 1

正如已经指出的那样，对您的问题的描述并不十分精确。 让我感到奇怪的事情之一就是为什么您的任何类的析构函数都会被调用。 查看您的代码，您会发现Enemy tmp是一个本地实例，在离开Level构造函数后会被清除。 Add_Enemy（）函数接收此本地对象的副本。 由于没有提供复制构造函数，因此调用character_image.load( "grafx/enemy1.gif" ); 将不会在复制构造函数中执行，因此您存储的Enemy对象将没有图像。

也许您应该考虑这样的事情：

Enemy* tmp = new Enemy( 1200 ); // dynamic allocation of Enemy
enemey.Add_enemy( tmp );       

如果您这样做，则需要更改向量以存储指向敌人对象的指针，例如std::vector< Enemy* >敌人。 不要忘记删除Enemy_control的析构函数中的动态分配对象。