解析和读取文本文件到数组

C++: Parsing and Reading Text File Into an Array

本文关键字:文件 数组 取文本 读取      更新时间:2023-10-16

我希望我能在这里找到一些帮助。我下周有个作业要交,包括从一个txt文件中读取一堆数据到一个数组中,然后把结果打印出来。数据格式如下:

"麦克白"、"莎士比亚","41.04","161","23"、"978-88-5985-004-5"

"圣诞颂歌","查尔斯·狄更斯","98.74","167","547","978-26-2885-780-7"。.

.

.

每行有6条信息,我需要存储这些信息以供以后使用。我应该写代码来计算文本的行数,以便创建一个大小正确的动态数组。我已经搞定了。我有39行条目。然后我应该创建一个函数来读取txt文件,并将所有数据保存到我创建的数组中相应的对象中。

我不知道该用什么方法,这几天我一直在找教程和解释。我在文件和解析方面的经验非常有限,所以如果我有点缺乏经验,请原谅。下面是我到目前为止的代码:

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

class Author
{
    public:
private:
    string fname, lname;
};
class Book
{
    friend ofstream& operator<<(ofstream&, Book);
        public:
        Book();
    private:
        string bookName;
        Author author;
        double price;
        int qtyOnHand;
        int qtySold;
        double revenue;
        string ISBN;
};
Book :: Book()
{
}
int getLineNumber(ifstream &);
void parseData(ifstream &, Book []);

//void sortBookList(Book[], int, int);

int main()
{
    int numberOfBooks;
    //open the file from which to read the data
    ifstream myFile;
    myFile.open("Book List.txt");
    //function to find out how many objects to create
    numberOfBooks = getLineNumber(myFile);
    //create an array with that many objects
    Book *bptr;
    bptr = new Book[numberOfBooks];
    //function to read information from file into array of objects
    parseData(myFile, bptr);
    //loop to call sorting function and output function based on 4 different criteria
    //close the file explicitly
    return 0;
}
int getLineNumber(ifstream &myFile)
{
    int counter = 0;
    string myString;

    while(!myFile.eof())
    {
        getline(myFile, myString);
        counter++;
    }
    myFile.close();
    counter --;
    return counter;
}
void parseData(ifstream &myFile, Book bookPtr[])
{
}

所以,总结我的问题,我不明白如何解析数据从文本文件到我的数组。事先非常感谢任何可以帮助你的人!欢呼。

编辑:我试着在代码上瞎混,我想我在正确的方向上迈出了一步,但我仍然有点迷路。下面是我为parseData函数准备的内容。

void parseData(ifstream &myFile, Book bookPtr[])
{
    string dummyLine;
    string word, line;
    myFile.open("Book List.txt");
    getline(myFile, dummyLine);
    string data[6];
    while(!myFile.eof())
    {
        getline(myFile, line, 'n');
        for (size_t i = 0; i < line.size(); ++i)
        {
            char c = line[i];
            if(c == ',' || c == 'n')
            {
                if(!word.empty())
                {
                    data[i] = word;
                    word.clear();
                }
            }
            else
            {
                word += c;
            }

        }
        if(!word.empty())
        {
            //cout << word << endl;
        }
    }


}

也许你只需要知道如何处理字符串中的每个字符?

下面是一些代码,它们遍历字符串中的每个字符来构建单词,然后分别打印它们。您会注意到stringvector (str[i], str.push_back(char), str.size()等)具有相同的接口。

// You'll need to include <iostream> and <string>
std::string example = "This is an example string";
std::string word;
// Notice how you can loop through a string just like a vector<char>
for(size_t i = 0; i < example.size(); ++i) {
    char c = example[i];
    // When we see whitespace, print the current word and clear it
    if(c == ' ' || c == 't' || c == 'n') {
        // Don't print anything if we don't have a word
        if(!word.empty()) {
            std::cout << word << std::endl;
            word.clear();
        }
    } else {
        // Append the current character to the end of the string
        word += c; // or word.push_back(c)
    }
}
// In case the line doesn't end with whitespace
if(!word.empty()) {
    std::cout << word << std::endl;
}

std::basic_string (std::string的别名)引用可能是有用的

可以使用一个向量数据结构来保存book类。向量记录;

(我强烈建议使用向量(或列表),因为它将避免文件的双重读取,因为您根本不需要知道行数)

解析具有固定数量字段的行,原则上很容易:

int counter = 0;
string myString;

while(!myFile.eof())
{
    getline(myFile, myString);
    counter++;
}
counter --;
//Clear the error state flag
myFile.clear()
//Return to the beginning of the file:
myFile.seekg(ios_base::beg);

const int fieldCount = 5;
string field[fieldCount ];

string buffer= "";
char c = '';
for( int i = 0; i < counter; ++i ) {
    for( int j = 0; j < fieldCount; ++j ) {
        myFile.ignore(); //Ignore the first '"'
        //Read each character up to the second '"'
        while( myFile.good() && (c = myfile.get()) != '"' ) {
            buffer += c;
        }
        field[j] = buffer;
        buffer = "";
        if( j != fieldCount - 1 ) {
            myFile.ignore(); //Ignore the first ','
        }
    }
    //Use the fields here.
}

我没有测试这段代码,我知道缺少错误测试,但是它显示了一种方法。