C++ 单独的头文件和源文件

Question

我是 C++ 的新手，到目前为止，我已经将所有代码都放在同一个文件中。现在，随着我的进步，我需要将我的代码分成我不太熟悉的源文件和头文件。

我可以让它处理简单的任务，但是在我现在尝试分成单独文件的这个程序中给我一个错误，而当我把它全部放在一个文件中时，我可以编译它。

我卡在错误信息上了

main.cpp:10:1: error: unknown type name 'textEditor'
textEditor siEditor;

如果有人能解释为什么我会遇到这个错误以及如何防止它，我们将不胜感激。我读到它可能与重复声明有关，但我不明白从哪里来的。

这是我的 main.cpp 的样子:

#include <iostream>
#include <fstream>

using namespace std;

#include "textData.h"
#include "textEditor.h"

textData siData;
textEditor siEditor;

int main() 
{
    cout << "\nWelcome to siEdit!" << endl;
    while (true) 
    {
        cout << "\nWhat would you like to do? \nNew file = n, Append = a, View = v, Quit = q: ";
        string toDo;
        cin >> toDo;

        if (toDo == "n")
        {
            siEditor.openText();
            cout << "Now editing the file: " << siData.fileName.c_str() << endl;
            cout << "Type '=!' to stop editing and save. \n " << endl;
            siEditor.writeText();
        }

        else if (toDo == "a")
        {
            siEditor.appendTextOpen();
            cout << "Now appending text: " << siData.appendTextfileName.c_str() << endl;
            cout << "Type '=!' to stop editing and save changes. \n " << endl;
            siEditor.appendText();
        }

        else if (toDo == "v")
        {
            siEditor.readText();
            cout << "\n";
        }

        else if (toDo == "q")
        {
            return 0;
        }

        else 
        {
            cout << "Invalid input." << endl;
        }
    }
}

siEdit.cpp:

#include <iostream>
#include <fstream>

using namespace std;

#include "textData.h"
#include "textEditor.h"

textData siData;

class textEditor
{
    public: 
    void openText()
    {   
        //when associated file is open. 
        while (siData.siFile.is_open())
        {
            siData.siFile.close();
        }
        cout << "\nWhat do you want to call your file? ";
        cin >> siData.fileName;

        //Creates / Opens fileEditor
        const char* path = siData.fileName.c_str();
        siData.siFile.open(path);
    }

    void writeText()
    {
        bool editing = true;
        bool hasEditing = false;

        while (editing == true)
        {
            //Get user input
            string input = " ";
            getline(cin, input);
            string yesNo;

            if (input == "=!") 
                {   
                    cout << "Would you like to save the file? Y/N" << endl;
                    cin >> yesNo;

                    if (yesNo == "Y")
                    {
                        cout << "Filed saved: " << siData.fileName.c_str();
                        editing = false;
                    }   

                    else if (yesNo == "N")
                    {
                        cout << "No changes have been saved. Exiting." << endl;
                        hasEditing = false;
                        editing = false;
                        siData.siFile.clear();
                    }

                    else 
                    {
                        cout << "Invalid input. Type '=! to exit." << endl;

                    }
                }       

            else
            {
                siData.siFile << input;
                siData.siFile << endl;
                hasEditing = true;
            }
        }
    }


    void readText()
    {
        string line;
        cout << "\nEnter the name of your file: ";
        cin >> siData.fileName;
        cout << "\n";
        const char* path = siData.fileName.c_str();

        // input file stream
        //Internal stream buffer which performes I/O on file.
        ifstream siFileRead(path);
        if(siFileRead.is_open())
        {
            while(getline(siFileRead,line))
            {
                cout << line << endl;
                siData.siFile << line;
            }
        }

        else
        {
            cout << "Unable to open file. Confirm name and file location.";
        }
    }

    // open the existing text file
    void appendTextOpen()
    {
        while (siData.siFileAppend.is_open())
        {
            // erase previous text
            siData.siFileAppend.clear();
            // close the input text file
            siData.siFileAppend.close();
        }

        cout << "\nEnter the name of the file: ";
        //find file name.
        cin >> siData.appendTextfileName;

        //Makes / Opens file
        const char* path = siData.appendTextfileName.c_str();
        siData.siFileAppend.open(path, fstream::app);
    }

    //add text together with previous input.
    void appendText()
    {
        bool editing = true;
        bool hasEditing = false;

        while (editing == true)
        {
            //Gets user input
            string input = " ";
            getline(cin, input);

            if (input == "=!")
            {
                if (hasEditing == true)
                {
                    cout << "File saved: " << siData.appendTextfileName.c_str() << endl;
                    editing = false;
                }
            }

            else
            {
                siData.siFileAppend << input;
                siData.siFileAppend << endl;
                hasEditing = true;
            }
        }
    }
};

文本数据.h:

#ifndef SIEDITOR_H
#define SIEDITOR_H

class textData
{
    public: 
        string fileName;
        string appendTextfileName;
        ofstream siFile;
        ofstream siFileAppend;
};

#endif

文本编辑器.h:

#ifndef SIEDITOR_H
#define SIEDITOR_H

class textEditor
{
    public: 
    void openText()
    void writeText()
    void readText()
    void appendTextOpen()
    void appendText()
};


#endif

Answer 1

您在两个头文件中使用相同的 include guard，即 SIEDITOR_H。这样可以防止包含第二个 header 的内容。使用 #pragma once 而不是包含保护符号。

#pragma once 是一个事实上的标准，即 supported by all compilers of practical interest .

在您的实现文件中不要重复类定义。只需定义声明的成员函数。和 static 数据成员，如果有的话。