Sort a vector of objects by an object's attribute [duplicate]

Question

Possible Duplicate:
How to use std::sort with a vector of structures and compare function?

I have a cat object (what?) and a catSort object which obviously sorts the cat objects. Below is the classes

class cat {
public:
    int age;
};

class catSorter {
public:
    vector< cat > cats;
    vector< cat > SortCatsByAge();
    void AddCat( cat new_cat );
};

void catSorter::AddCat(cat new_cat){
    this->cats.push_back(new_cat)
}

vector< cat > catSorter::SortCatsByAge(){
    // Sort cats here by age!
}


cat tim;
tim.age = 10;

cat mark;
mark.age = 20

cat phil;
phil.age = 3;

catSorter sorter;
sorter->AddCat(tim);
sorter->AddCat(mark);
sorter->AddCat(phil);

std::<vector> sortedcats = sorter->SortCatsByAge();

I'm having difficulties sorting a vector, how would I go about doing this? Should I just loop through the cats attribute and store them inside a temporary vector then return that? Is there an easier way to do this?

Answer 1

You should implement an operator< on cat so that cats can be sorted:

class cat {
public:
    int age;
    bool operator< (const cat &other) const {
        return age < other.age;
    }
};

You can then include the "algorithm" header and use std::sort on your array:

vector< cat > catSorter::SortCatsByAge(){
   vector< cat > cats_copy = cats;
   std::sort(cats_copy.begin(), cats_copy.end());
   return cats_copy;
}