将此程序从 1 个功能转换为模块化的多功能程序？

Question

我对 C++ 非常陌生，并且有一个程序，我将其包含在下面。

我正在处理的程序从输入文件中读取文本并计算文本中每个字母的单词数和出现次数，然后打印结果。我的程序运行良好，但问题是所有代码都编写在主函数中，我需要将其分解为更多函数以使程序模块化，但我不确定如何去做。

我相信这很简单，但我不知道从哪里开始。我正在考虑实现两个 void 函数，一个用于读取/解释从数据文件中读取的内容，另一个用于显示结果；然后在主函数中调用它们，但我不确定这些函数的参数是什么。

int main()
{
    // Declaring variables
    char c; // char that will store letters of alphabet found in the data file
    int count[26] = {0}; // array that will store the # of occurences of each letter
    int words = 1; // int that will store the # of words
    string s; // declaring string found in data file

    // Opening input file stream
    ifstream in;
    in.open("word_data.txt");

    // Reading text from the data file
    getline(in, s);
    //cout << s << endl;

    // If input file fails to open, displays an error message
    if (in.fail())
    {
        cout << "Input file did not open correctly" << endl;
    }


    // For loop for interpreting what is read from the data file
    for (int i = 0; i < s.length(); i++) {

        // Increment word count if new line or space is found
        if (s[i] == ' ' || s[i] == '\n')
            words++;

        //If upper case letter is found, convert to lower case.
        if (s[i] >= 'A' && s[i] <= 'Z')
            s[i] = (tolower(s[i]));

        //If the letters are found, increment the counter for each letter.
        if (s[i] >= 'a' && s[i] <= 'z')
            count[s[i] - 97]++;
    }


    // Display the words count
    cout << words << " words" << endl;

    // Display the count of each letter
    for (int i = 0; i < 26; i++) {
        if (count[i] != 0) {
            c = i + 97;
            cout << count[i] << " " << c << endl;
        }
    }
         
    // Always close opened files
    in.close();

    return 0;

}

Answer 1

我会像这样重写它：

class FileReader {
public:
    FileReader() {
        // Any init logic goes here...
    }
    ~FileReader() {
        // Always close opened files.
        in.close();
    }

    void open(std::string &filePath) {
        in.open(filePath);
    }

    std::string readLine() {
        std::string s;
        getline(in, s);
        return s;
    }

    bool hasErrors() const { // remove const if you get compile-error here.
        return in.fail();
    }

private:
    ifstream in;
};

class LetterCounter {
public:
    void process(std::string &s) {
        // For loop for interpreting what is read from the data file
        for (int i = 0; i < s.length(); i++) {
            // Increment word count if new line or space is found
            if (s[i] == ' ' || s[i] == '\n')
                words++;

            //If upper case letter is found, convert to lower case.
            if (s[i] >= 'A' && s[i] <= 'Z')
                s[i] = (tolower(s[i]));

            //If the letters are found, increment the counter for each letter.
            if (s[i] >= 'a' && s[i] <= 'z')
                count[s[i] - 97]++;
        }
    }

    void logResult() {
        char c; // char that will store letters of alphabet found in the data file.

        // Display the words count
        cout << words << " words" << endl;

        // Display the count of each letter
        for (int i = 0; i < 26; i++) {
            if (count[i] != 0) {
                c = i + 97;
                cout << count[i] << " " << c << endl;
            }
        }
    }

private:
    int count[26] = {0}; // array that will store the # of occurences of each letter
    int words = 1; // int that will store the # of words
};

int main()
{
    // Opening input file stream.
    FileReader reader;
    reader.open("word_data.txt");

    // Reading text from the data file.
    std::string s = reader.readLine();

    // If input file fails to open, displays an error message
    if (reader.hasErrors()) {
        cout << "Input file did not open correctly" << endl;
        return -1;
    }

    LetterCounter counter;
    counter.process(s);
    // Display word and letter count.
    counter.logResult();
    
    return 0;
}

注意，我没有测试就写了（请原谅任何错误），
但这应该让您大致了解它应该是怎样的。