Thread: Sorting Vector of structs.

It goes where the /*goes here comment*/ was before; you need the begin, you need the end, and then you need something that, if you put () after it compares the things.

Would something like this work.

Code:

std::sort(myElections->at(i)->myCandidates->begin(), myElections->at(i)->myCandidates->end(), Election::Candidate::operator ());

Didn't we start here? The third parameter needs to be a function object. I.e., it needs to be something that has an operator(), not an operator() itself. I.e., it needs to be an object of type Election::Candidate, so that when operator () is applied to it, the Election::Candidate:perator() you defined comes out.

(I mean, maybe operator() will work if it can accept a function pointer in the third spot in place of a function object, but I've never tried.)

What would I place in the third parameter exactly or what pointer could I get rid of to make it easier.

If it were me, I would have called my sorting function

Code:

bool operator<(const Election::Candidate*& lhs , const Election::Candidate*& rhs)

made it a free function (i.e., not in a class), made it a friend if necessary, and not used the third parameter to sort at all.

If for some reason I'm not allowed to overload that operator, I'd make it its own object:

Code:

class Bob {
    operator () {const Election::Candidate*& lhs , const Election::Candidate*& rhs) //etc
}

and just used Bob for the third parameter.

Where would I overload the operator< at. Outside or inside the class, and If so how does it know to use that operator overload.

The compiler gives me this final error

Code:

bool operator<(const View::Election::Candidate*& lhs , const View::Election::Candidate*& rhs){
	return *lhs->myTotalNumberOfVotes < *rhs->myTotalNumberOfVotes;
}

'operator <' must have at least one formal parameter of class type

I was afraid of that. (Reason 347 not to use pointers -- you can't overload.) Then you'll have to go with curtain 2 and a function object.

which pointer messes it up. I can change it.

The vector-of that we're trying to sort. Since we're trying to sort pointers, the compiler gives us a frowny face, because pointers are built-in types. If we were trying to sort Election::Candidates themselves, we could define operator<.

Those are the only pointers that I have to have for the assignment. Would having the class that just has the operator< work with the pointers.

Then you'll have to go with class Bob and the function object.

Code:

#ifndef COMPARATOR_H
#define COMPARATOR_H
#include "View.h"
class Comparator{
	bool operator () (const View::Election::Candidate*& lhs , const View::Election::Candidate*& rhs){

		return *lhs->myTotalNumberOfVotes < *rhs->myTotalNumberOfVotes;
	}
};
#endif

Is that what I would have to do.