C++：无法修改全局变量

Question

我现在正在做一项作业，在将数据组的新成员添加到链表时遇到了一些困难。我已经用谷歌搜索并查看了所有内容，但我无法找到解决问题的方法。问题是，当我在Openbutton_Click中打开文件时，我全局声明的 6 个变量（客户和 5 个节点类型变量）最初会被修改。但是我无法在addconf_Click晚些时候修改变量。通常我不会发布寻求帮助，但我的时间不多了，无法弄清楚这一点。我在格式化时遇到了很多麻烦，所以请耐心等待。

这是 myform.h 附带的.cpp文件

#include "MyForm.h"
using namespace System; 
using namespace System::Windows::Forms; 
using namespace std;
int customers = 0;
node *current;
node *first;
node *last;
node *temp;
node *previous;

[STAThread] 
void Main(array<String^>^ args) { 
Application::EnableVisualStyles(); 
Application::SetCompatibleTextRenderingDefault(false); 
Project1::MyForm form;
Application::Run(%form); 
}

这一切都在myform.h中

#pragma once
#include <fstream>
#include <string>
#include <iostream>
#include <sstream>
#include <msclrmarshal_cppstd.h>
#include "header.h"
using namespace std;
struct node{
account customer;
node *next;
};
extern int customers;
extern node *current;
extern node *first;
extern node *last;
extern node *temp;
extern node *previous;
private: System::Void Openbutton_Click(System::Object^  sender, System::EventArgs^  e) {
ifstream fin;
openFileDialog1->ShowDialog();
String^ filenname = System::IO::Path::GetFileName(openFileDialog1->FileName);
std::string filename = msclr::interop::marshal_as<std::string>(filenname);
fin.open(filename);

if (fin){
    this->label2->Text = "File Opened";
}
else
    this->label2->Text = "Failed to Open File";
String^ menu;
String^ temp;
string input;
string name;
string numstr;
string pinstr;
string balstr;
int num;
int pin;
float bal;
first = new node;
getline(fin, input);
numstr = input.substr(0, 3);
stringstream convert3(numstr);
convert3 >> num;

name = input.substr(8, 16);
name.erase(name.find_last_not_of(" nrt") + 1);
pinstr = input.substr(24, 4);

balstr = input.substr(30, 7);

stringstream convert(pinstr);
convert >> pin;
stringstream convert2(balstr);
convert2 >> bal;
first->customer.setNum(num);
first->customer.setName(name);
first->customer.setPin(pin);
first->customer.setBal(bal);
first->next = 0;
numstr.clear();
name.clear();
pinstr.clear();
balstr.clear();
current = first;
customers++;
while (fin){
    customers++;
    previous = current;
    current->next = new node;
    current = current->next;
        getline(fin, input);
        numstr = input.substr(0, 3);
        name = input.substr(8, 16);
        name.erase(name.find_last_not_of(" nrt") + 1);
        pinstr = input.substr(24, 4);
        balstr = input.substr(30, 7);
        stringstream convert3(numstr);
        convert3 >> num;
        stringstream convert(pinstr);
        convert >> pin;
        stringstream convert2(balstr);
        convert2 >> bal;

        current->customer.setNum(num);
        current->customer.setName(name);
        current->customer.setPin(pin);
        current->customer.setBal(bal);
    }
    last = previous;
    last->next = 0;
    customers--;
    cout << "All accounts loaded, system ready." << endl;
    // Print and fill the textbox
    current = first;
    menu = "Account List:" + customers + "rn " + "Num | Account Holder | Pin | Balancern";

    for (int c = 0; c < customers; c++){
        menu += current->customer.getNum();
        menu += " | ";
        temp = gcnew String(current->customer.getName().c_str());
        menu += temp;
        menu += " | ";
        menu += current->customer.getPin();
        menu += " | $";
        menu += current->customer.getBal();
        menu += "rn";
        if (current->next != 0){
            current = current->next;
        }
        else
            c = customers;
    }

textBox1->Text = gcnew String(menu);
launch->Visible = true;
addCust->Visible = true;
remCust->Visible = true;
refList->Visible = true;
}
private: System::Void addconf_Click(System::Object^  sender, System::EventArgs^  e) {
int num = -1;
string name = "";
int pin = -1;
float bal = -1;
bool match = false;
string numstr = msclr::interop::marshal_as<std::string>(addnumbox->Text);
num = stoi(numstr);
name = msclr::interop::marshal_as<std::string>(addnamebox->Text);

name.erase(name.find_last_not_of(" nrt") + 1);
string pinstr = msclr::interop::marshal_as<std::string>(addpinbox->Text);
pin = atoi(pinstr.c_str());
string balstr = msclr::interop::marshal_as<std::string>(addbalbox->Text);
bal = stof(balstr);
if (num != -1 && pin != -1 && name != "" && bal != -1){
    current = new node;
    last->next = current;
    current->customer.setNum(num);
    current->customer.setName(name);
    current->customer.setPin(pin);
    current->customer.setBal(bal);
    current->next = 0;

    last = current;
    customers = customers + 1;
    num = -1;
    pin = -1;
    name = "";
    bal = -1;

    }

}

标题.h 在这里

#include <string>
#include <iostream>
using namespace std;

class account{
private:
int accNum;
int accPin;
string accName;
float accBal;
public:
void setNum(int num);
void setPin(int pin);
void setName(string name);
void setBal(float bal);
void deposit(float money);
void withdraw(float money);
int getNum();
int getPin();
string getName();
float getBal();
};
void account::setNum(int num){
accNum = num;
}
void account::setPin(int pin){
accPin = pin;
}
void account::setName(string name){
accName = name;
}
void account::setBal(float bal){
accBal = bal;
}
int account::getNum(){
return accNum;
}
int account::getPin(){
return accPin;
}
string account::getName(){
return accName;
}
float account::getBal(){
return accBal;
}
void account::deposit(float money){
accBal = accBal + money;
}
void account::withdraw(float money){
accBal = accBal - money;
}

Answer 1

您在头文件中将customers声明为 int。请记住，头文件是文学粘贴到它所包含的文件中的。因此，您将拥有该变量的许多实例。

正确的方法是在 cpp 文件中定义它，并通过在头文件中使用 extern int customers 使其全局化。

对于您的nodes变量也是如此。您必须在 cpp 文件中定义它们，以便它们只存在于一个位置。

但是，使用这样的全局可变变量几乎从来都不是一个好主意。

Answer 2

事实证明，

我缺少一行代码，无法正确打印出列表的当前状态。现在感觉自己像个彻头彻尾的白痴。感谢你们中那些帮助过的人。