我无法将文本文件中的数据传递到队列

Question

我正在创建一个程序，它将存储我的文本文件中的数据并将其排入队列。我已经为它创建了一个函数，但是它不会将数据存储到我的队列中。

这是我从文本文件中获取数据并将其插入队列的函数：

void TextToQueue() {
    Queue<Information> link; //Connecting my Queue to my structure called Information
    Information TextInfo; //Information is a structure containing string Name, Address, and ID
    Temp_File t; //Temp_File is a structure containing string data and type.
    fstream FILE;
    int i = 0;
    char delimiter = ':';
    char delimiter1 = '\n';
    FILE.open("Sample.txt", ios::in);
    if (FILE.is_open()) {
        while (getline(FILE, t.type, delimiter) && getline(FILE, t.data, delimiter1)) {
            if (i == 0) { 
                TextInfo.Name = t.data; //The data inside my t.data will be stored in TextInfo.Name
                i++;
            }
            else if (i == 1) {
                TextInfo.Address = t.data; //The data inside my t.data will be stored in TextInfo.Address
                i++;
            }
            else if (i == 2) {
                TextInfo.ID = t.data; //The data inside my t.data will be stored in TextInfo.ID
                link.push(TextInfo); //Pushing or Enqueuing the data to my queue
                i = 0; //the value of i will become zero again to repeat the whole process whenever there are a lot of data inside the file.
            }
        }
        FILE.close();
    }
    else {
        std::cout << "File is not open.";
    }
}

这是我将数据存储到队列的推送功能。每当我将新数据插入文本文件时，推送功能都会起作用，但是我认为问题出在 TextToQueue 函数中：

template <class T>
void Queue<T>::push(T data) {
    Queue* tmp = new Queue;
    tmp->value = data;
    tmp->next = NULL;
    if (!front) {
        rear = tmp;
        front = tmp;
    }
    else {
        rear->next = tmp;
        rear = tmp;
    }
}

Answer 1

您的问题是循环和 if 语句的本地范围。每次将属性分配给Information 时，都会调用构造函数。解决方案是使用auto TextInfo = new Information 构造函数，推送它，然后将TextInfo 重新分配给一个新对象。只需要考虑销毁创建的对象。或者您可以将TextInfo 推送到队列中，然后只需修改属性并在最后一个子句中推送一个新的空白。

Answer 2

link 是一个不返回的局部变量。您无法从函数外部访问它。解决您的问题的一种方法是通过引用 TextToQueue 传递一个队列，将其填充到函数内部并在函数外部读取它：

#include <fstream>
#include <iostream>
#include <string>

template <class T>
struct Queue {
    T value;
    Queue* front;
    Queue* rear;
    Queue* next;
    void push(T data);
};

template <class T>
void Queue<T>::push(T data) {
    Queue* tmp = new Queue;
    tmp->value = data;
    tmp->next = NULL;
    if (!front) {
        rear = tmp;
        front = tmp;
    }
    else {
        rear->next = tmp;
        rear = tmp;
    }
}

struct Information {
    std::string ID;
    std::string Name;
    std::string Address;
};
struct Temp_File {
    std::string type;
    std::string data;
};

void TextToQueue(Queue<Information> &link) {
    Information TextInfo; //Information is a structure containing string Name, Address, and ID
    Temp_File t; //Temp_File is a structure containing string data and type.
    std::fstream FILE("Sample.txt", std::ios::in);
    int i = 0;
    char delimiter = ':';
    char delimiter1 = '\n';
    if (FILE.is_open()) {
        while (getline(FILE, t.type, delimiter) && getline(FILE, t.data, delimiter1)) {
            if (i == 0) { 
                TextInfo.Name = t.data; //The data inside my t.data will be stored in TextInfo.Name
                i++;
            }
            else if (i == 1) {
                TextInfo.Address = t.data; //The data inside my t.data will be stored in TextInfo.Address
                i++;
            }
            else if (i == 2) {
                TextInfo.ID = t.data; //The data inside my t.data will be stored in TextInfo.ID
                link.push(TextInfo); //Pushing or Enqueuing the data to my queue
                std::cout << "push\n";
                i = 0; //the value of i will become zero again to repeat the whole process whenever there are a lot of data inside the file.
            }
        }
        FILE.close();
    }
    else {
        std::cout << "File is not open.";
    }
}

int main() {
    Queue<Information> link; //Connecting my Queue to my structure called Information
    TextToQueue(link);
    std::cout << "Data: \n";
    std::cout << '"' << link.front->value.ID << "\"\n";
    std::cout << '"' << link.front->value.Name << "\"\n";
    std::cout << '"' << link.front->value.Address << "\"\n";
}

文件：

id:ID
name:Name
address:Address

输出：

Data: 
"Address"
"ID"
"Name"