c++ 遍历对象数组

Question

Im newbie in c++ and im having hard times with looping through array of objects. Objects are in this form: Class * arr; (in my case: Persons * person_list; )

PROBLEM: I have no idea how to loop through object array, i want to call functions on them, for example, as you can see my code has Persons class with function printPersonsInfo() and i have array decleration in main file ( array personList), i want to be able to do something like for(Persons p: personList) p.printPersonInfo();

Tried to make many kind of loops, unsuccessful for loops with unsuccessful size of arrays, nothing works so far. Here comes the code:

Main file:

int main()
{

    //reading objects from file into array
    Persons * personList = Files::createPersonsArray();

    //reading objects from file into array
    Auto * autoList = Files::createAutoArray();

    return 0;
}

One of Object classes ( both are pretty much the same):

class Persons
{
public:
    int id;
    string name, surename, phone;

    Persons() {
        //required empty constructor
    }

    Persons(int i, string n, string s, string p) {
        this->id = i;
        this->name = n;
        this->surename = s;
        this->phone = p;
    }


    void printPersonInfo() {
        cout << endl;
        cout << "ID : " << id << endl;
        cout << "Name : " << name << endl;
        cout << "Surename : " << surename << endl;
        cout << "Phone : " << phone << endl;
    }

};

Files.h class, where i read data from files and generate them into arrays:

class Files
{
public:

    static Persons * createPersonsArray() {

        string textLine;

        // Read from the text file
        ifstream PersonsFile("Persons.txt");

        //counter
        int count = 0;
        //counting records in file
        while (getline(PersonsFile, textLine))
            count++;

        //return to start of file
        PersonsFile.clear();
        PersonsFile.seekg(0, ios::beg);

        //making array of persons
        Persons* person_list = new Persons[count];

        //total persons found
        cout << "Lines of persons :" << count << endl;

        int i = 0;
        // Use a while loop together with the getline() function to read the file line by line
        while (getline(PersonsFile, textLine)) {

            //explodes line of person info into parts
            auto parts = explode(  textLine,'#');

            //stoi converts ID from string to int
            person_list[i] = Persons(stoi(parts[0]), parts[1], parts[2], parts[3]);

            //increased counter
            i++;
        }

        // Close the file
        PersonsFile.close();

        return person_list;
    }

    static Auto* createAutoArray() {

        string textLine;

        // Read from the text file
        ifstream AutoFile("Auto.txt");

        //counter
        int count = 0;
        //counting records in file
        while (getline(AutoFile, textLine))
            count++;

        //return to start of file
        AutoFile.clear();
        AutoFile.seekg(0, ios::beg);

        //making array of persons
        Auto* auto_list = new Auto[count];

        //total persons found
        cout << "Lines of autos :" << count << endl;

        int i = 0;
        // Use a while loop together with the getline() function to read the file line by line
        while (getline(AutoFile, textLine)) {

            //explodes line of person info into parts
            auto parts = explode(textLine, '#');

            //stoi converts ID from string to int
            auto_list[i] = Auto(stoi(parts[0]), stoi(parts[1]), stoi(parts[2]), parts[3], parts[4], parts[5]);

            //increased counter
            i++;
        }

        // Close the file
        AutoFile.close();

        return auto_list;
    }


    //explode function
    static vector<string> explode(string const& s, char delim)
    {
        vector<string> result;
        istringstream iss(s);

        for (string token; getline(iss, token, delim); )
        {
            result.push_back(move(token));
        }

        return result;
    }


    //find owner info based on id
    static void findCarOwnerInfo(int id) {

        string textLine;

        // Read from the text file
        ifstream PersonsFile("Persons.txt");

        //if file is not empty
        if (PersonsFile.peek() != ifstream::traits_type::eof()) {

            //counting records in file
            while (getline(PersonsFile, textLine)) {
                 auto parts = explode(textLine, '#');

                 //if person id matches
                 if (stoi(parts.at(0)) == id) {
                     cout << endl;
                     cout << "(ID:"<<parts.at(0)<<") Owner info ---------" << endl;
                     cout << "Name : " << parts.at(1) << endl;
                     cout << "Surename : " << parts.at(2) << endl;
                     cout << "Phone : " << parts.at(3) << endl;
                 }
            }
        }
        else {
            cout << "error finding persons." << endl;
        }
    }
};

Since i shared Persons class and reading from files, here is how i store my info in Persons.txt:

ID#NAME#SURENAME#PHONE

The idea is to read files, create arrays of objects from them and pass them to the main class.

Im using C++14 if that makes any difference.

Thanks.

Answer 1

You should just return a std::vector instead of a raw pointer. The raw pointer do not brings with it the number of elements it points to (you'd need an extra parameter for that). Then you can iterate as usual on the vector.

Answer 2

Looping through an array of objects can be done as such

Persons personList[constSize];
for (int i=0; i<=constSize; ++i){
    personList[i].func();
}

or if you are unsure of the necessary size of the array

vector<Persons> personList;
Persons x;
while(getline(PersonsFile, textLine)){
    personList.pushback(x);
}
personList[0].func();

A copy of the Persons object "x" will be appended to the vector for each line in your file.