我正在开发一个项目，我将前向列表和向量一起使用并输出它们的值。转发列表是Frame个对象的列表，向量是Display个对象的向量。问题是在InsertFrame()中创建对象之后，向量的值会丢失并且基本上变成垃圾。我可以在调试器中看到它在函数结束后发生，这使我相信它与超出范围的变量有关。这是主要的创作类
// Animation.cpp
#include <crtdbg.h>
#include <iostream>
#include <string>
#include <vector>
#include <forward_list>
using namespace std;
#include "Display.h"
#include "Frame.h"
#include "Animation.h"
#include "GPUMemoryDisplay.h"
#include "SystemMemoryDisplay.h"
void Animation::InsertFrame() {
int numDisplays; //for user input of display number
vector <Display*>v; //vector for containing display objects
int p_x; //will contain user input for pixel_x
int p_y; //will contain user input for pixel_y
int p_duration; //will contain user input for duration
int p_type ; //will contain display type as int value
char * p_name; //temp string to contain user input for name
string d_name; //will contain p_name to be passed to display constructor
string frameName; //contains user input for the frame name
string gpu_shader; //contains gpu name if gpu type is selected
int q = 0; //used to count the diplay #
//begin reading user input
cout << "Insert a Frame in the Animation\nPlease enter the Frame filename: ";
cin >> frameName;
cout << "Entering the Frame Displays (the sets of dimensions and durations) " << endl;
cout << "Please enter the number of Displays: ";
cin >> numDisplays;
//display creation loop for # of displays entered
while (numDisplays > 0) {
cout << "Please enter pixel x-width for Display #" << q << " pixel_x:";
cin >> p_x;
cout << "Please enter pixel y-width for Display #" << q << " pixel_y:";
cin >> p_y;
cout << "Please enter the duration for this Display: ";
cin >> p_duration;
cout << "Please enter the name for this Display: ";
cin >> d_name;
cout << "Please enter the type for this display (1 = SystemMemoryDisplay, 2 = GPUMemoryDisplay): ";
cin >> p_type;
p_name = new char[d_name.length() + 1]; //allocate for the size of the name entered
strcpy(p_name, d_name.c_str()); //copy string to char []
if (p_type == 2) {
//input for GPU shader
cout << "Please enter the file name of the associated GPU Shader: ";
cin >> gpu_shader;
Display *gpu_p = new GPUMemoryDisplay(p_x, p_y, p_duration, p_name, gpu_shader);
v.push_back(static_cast <Display*>(gpu_p)); //casting to a display* and pushing onto the vector
numDisplays--;
q++;
}
else {
Display *sm_p = new SystemMemoryDisplay(p_x, p_y, p_duration, p_name);
v.push_back(static_cast <Display*>(sm_p));//casting to a display* and pushing onto the vector
numDisplays--;
q++;
}
cout << "\n";
}
Frame t_frame = Frame(frameName, v); //new frame holds vector which contains displays
//check if forward list is empty
if (frames.empty()) {
cout << "\nThis is the first Frame in the list \n\n";
frames.push_front(t_frame);
}
else {
forward_list <Frame>::iterator it;
int x = 0; // used for size of current forward_list
//iterate forward list to obtain the size
for (it = frames.begin(); it != frames.end(); ++it) {
x++;
}
if (x == 1) {
it = frames.begin();
frames.insert_after(it, t_frame);
}
else {
cout << "There are " << x << " Frame(s) in the list\n" << "Please specify the position, between 0 and " << x << " to insert after : ";
cin >> x; //read in where user wants to put the frame
//iterate to desired position and insert
forward_list <Frame>::iterator it;
it = frames.begin();
while (x != 0 && it != frames.end()) {
it++;
x--;
}
frames.insert_after(it, t_frame);
}
}
}
框架和显示的标题/ cpp文件
// Frame.h
#pragma once
class Frame
{
string fileName;
vector<Display*> displays;
public:
Frame(string s, vector<Display*> d) :fileName(s), displays(d) {}
Frame(const Frame&);
~Frame()
{
vector<Display*>::iterator it;
for (it = displays.begin(); it != displays.end(); it++)
delete *it;
}
friend ostream& operator<<(ostream&, Frame&);
};
#pragma once
// Display.h
class Display
{
protected: // accessible to derived classes
int pixel_x;
int pixel_y;
int duration;
char* name;
public:
Display(int x, int y, int duration, char* name);
Display(const Display&);
virtual ~Display() //makes class abstract, cannot be instantiated, most general class
{
if (name)
delete[]name;
}
virtual int BufferSize() = 0; // overridden function Polymorphic function
friend ostream& operator<<(ostream&, Display&);
};
// Display.cpp
#include <crtdbg.h>
#include <iostream>
#include <string>
#include <vector>
#include <forward_list>
using namespace std;
#include "Display.h"
#include "GPUMemoryDisplay.h"
Display::Display(int x, int y, int d, char* n) :pixel_x(x), pixel_y(y), duration(d), name(n) {
}
Display::Display(const Display& p) {
//copy values from p
pixel_x = p.pixel_x;
pixel_y = p.pixel_y;
duration = p.duration;
size_t len = strlen(p.name);
name = new char[len + 1];
strcpy(name, p.name);
//cout << pixel_x << pixel_y << duration << name;
}
我有两个名为GPUMemoryDisplay和SystemMemoryDisplay的子类，但我相信部分代码很好，因为我可以看到它们的值在调试器中正确存储。以下是以防万一。
#pragma once
// SystemMemoryDisplay.h
class SystemMemoryDisplay : public Display
{
public:
SystemMemoryDisplay(int x, int y, int duration, char* name) :Display(x, y, duration, name) {};
SystemMemoryDisplay(const SystemMemoryDisplay& RGMD) :Display(RGMD) {}
int BufferSize() { return pixel_x*pixel_y * sizeof(double); }
};
#pragma once
//GPUMemoryDisplay.h
//this is the derived class of display
class GPUMemoryDisplay : public Display
{
string shader;
public:
GPUMemoryDisplay(int x, int y, int duration, char* name, string shader) :Display(x, y, duration, name), shader(shader) {};
GPUMemoryDisplay(const GPUMemoryDisplay& RGPUMD) :shader(RGPUMD.shader), Display(RGPUMD) {}
string GetShader() { return shader; }
int BufferSize() { return pixel_x*pixel_y * sizeof(float); } //this is the overridden function from Display class
};
总之，我有一个前向的帧列表，每个帧都可以包含一个Display对象的向量。但是，当InsertFrame（）函数退出时，显示数据将丢失。
答案 0 :(得分：2)
一旦堆栈分配的Frame t_frame = Frame(frameName, v);对象超出范围，它们的析构函数就会被调用，并将删除存储在Frame::displays中的指针所指向的所有对象。您需要实现适当的复制和/或移动构造函数和赋值运算符，以便正确地传递这些指针。您应该使用::std::unique_ptr来保留已分配对象的所有权，而不是使用原始指针并手动删除它们，并::std::string来管理字符串而不是指向char的原始指针。同时将using namespace std;置于中间包含也不好，如果你打算在包括之后至少使用