我从另一个类(B类)函数调用类(A类)函数时遇到问题,其中函数在函数之后删除了我试图调用的类(A类)中构造的变量完成并返回到我调用的函数(C类)。发生了什么,我该如何解决这个问题?
我已经尝试使用指向该类的指针并动态分配整个类,但变量仍然被删除。
#include <iostream>
#include <vector>
#include <string>
#include <ctime>
using namespace std;
class A {
private:
vector<string> vectorA;
string stringA[5] = { "1", "2", "3", "4", "5" };
string stringB[5] = { "6", "7", "8", "9" };
public:
string generaterandnum() {
int num1 = NULL;
num1 = rand() % vectorA.size();
string card = vectorA[num1];
vectorA.erase(vectorA.begin() + num1);
return card;
}
void buildvectorA()
{
for (int i = 0; i < 5; i++) {
for (int j = 0; j < 5; j++) {
vectorA.push_back(stringA[j] + stringB[i]);
}
}
return;
}
};
class B {
private:
vector<string> vectorB;
vector<string> vectorC;
A aobject;
public:
void buildvectorBandC() {
for (int i = 0; i < 5; i++) {
vectorB.push_back(aobject.generaterandnum());
}
for (int i = 0; i < 5; i++) {
vectorC.push_back(aobject.generaterandnum());
}
}
void displayvector() {
cout << "Vector: ";
for (size_t i = 0; i < vectorB.size(); i++) {
cout << "[" << vectorB[i] << "] (" << i << ") ";
}
cout << endl;
}
};
class C {
friend int main();
void programrun(int option) {
A* a = new A;
a->buildvectorA();
B* b = new B;
if (option == 0) {
cout << "Here is the vector that just has been constructed" << endl;
b->buildvectorBandC();
while (true) {
b->displayvector();
}
}
}
};
int main() {
srand((unsigned int)time(NULL));
cout << "Hello" << endl;
cout << "Enter (R) to run the program." << endl;
char input;
while (true) {
cin >> input;
input = toupper(input);
if (input == 'R') {
C cobject;
cobject.programrun(0);
return false;
}
else {
cout << "Invalid input" << endl;
}
}
}
我期望用随机生成的数字构建向量B和C,从vectorA中选择变量。但是我得到的是当它生成出兰德()时,它会在Project1.exe中显示0x00F1C77F处的未处理异常错误:0xC0000094:整数除零。因为vectorA的大小为0,因为它在程序离开该类的范围后被删除。
只要您的类对象执行,类成员就会活动。问题不在于对象的生命周期,而是因为B::aobject
从来没有调用buildvectorA
,所以它的vectorA
是空的,所以vectorA.size() == 0
。然后你试着计算rand() % vectorA.size()
,并且0
的(整数)除法是一个非常糟糕的主意。
您可能想为qazxsw poi创建一个构造函数,并在那里调用qazxsw poi以确保它始终正确:
A
请注意,generaterandnum
现在是私有方法。我们不希望外面的任何人打电话给它,因为他们不关心如何生成随机数。他们只想得到那些随机数。
这也意味着你的类class A {
private:
vector<string> vectorA;
string stringA[5] = { "1", "2", "3", "4", "5" };
string stringB[5] = { "6", "7", "8", "9" };
void buildvectorA()
{
for (int i = 0; i < 5; i++) {
for (int j = 0; j < 5; j++) {
vectorA.push_back(stringA[j] + stringB[i]);
}
}
}
public:
A() {
buildvectorA();
}
string generaterandnum() {
int num1 = NULL;
num1 = rand() % vectorA.size();
string card = vectorA[num1];
vectorA.erase(vectorA.begin() + num1);
return card;
}
};
不需要调用buildvectorA
,事实上,它甚至不需要任何对象C
。