c++ - Sort a vector of objects -

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i'm working simple c++ program, class: (i'm beginner programmer)

class car{ private:     string newbrand;     int newmileage;     int newyear;     double newprice;

(i didn't post public classes)

bool sortbyname(car &carvector)  {      return carvector.getbrand() < carvector.getbrand();  }

main:

int main(){      vector<car> carvector;     readfile(carvector);     listcar(carvector);      return 0; }

list car functions, when call function "sort", order vector of objects name:

void listcar(vector<car>&carvector){      int i, op;     system("cls");      sort(carvector.begin(), carvector.end(), sortbyname);      cout << "menu::car list name" << endl;     cout << ":brand: \t:mileage: \t:year: \t\t:price:" << endl;      for(i=0; i<carvector.size();i++)     {         cout << carvector[i].getbrand() << " \t\t";         cout << carvector[i].getmileage() << " \t\t";         cout << carvector[i].getyear() << " \t\t";         cout << carvector[i].getprice() << " \t\t";         cout << endl;     }          {     cout << endl << "1.back: ";     cin >> op;     }while(op!=1); }

i think program supposed work. can me finding error? best regards

in compare function, need use two parameters: should compare these objects each other. also, that's independent of vector (it operates on elements of vector), shouldn't name arguments avoid confusion.

so function this:

bool sortbyname(car &a, car &b)  {      return a.getbrand() < b.getbrand();  }

additionally, it's choice (but not required) add const parameteres passed reference in order indicate function body doesn't modify them:

bool sortbyname(const car &a, const car &b)  {      return a.getbrand() < b.getbrand();  }

but it's necessary put const @ end of signature of function car::getbrand() in order indicate that function won't modify object operates on. called const-correctness. mentioned before, process not required (like when using std::sort) it's style have const-correctness.

or can use lambda if compiler supports (you need enable c++11 support):

std::sort(carvector.begin(), carvector.end(), [](const car &a, const car &b){     return a.getbrand() < b.getbrand(); });

note if you're going compare cars always name, makes sense implement operator< class. when doing that, don't need specify compare function in call std::sort, objects compared a < b instead of yourfunction(a, b).


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