Vector sorting with different objects in it

[tokillmob]

Hello all, I am trying to come out with a sort function, previously, with some help, manage to do a sort that sorts base on a variable that is stored into an object vector.

PointTwoD is my object.

bool compare(const PointTwoD& a, const PointTwoD& b)
{ 
	return a.getcivIndex() > b.getcivIndex();
	//sort from high to low	
}

//to do the sort, i will just have to call it in my function
void Sort(vector<PointTwoD>& Vector)
{
         sort(Vector.begin(), Vector.end(), compare);
}

Base on this, i tried to recreate it.

ShapeTwoD is my object now, which is also a parent class.
I have 3 sub classes for polymorphism which i store the sub class objects into the vector.

bool compareAscend(ShapeTwoD& a, ShapeTwoD& b)
{ 
	return b.getArea() > a.getArea();		
}

bool compareDescend(ShapeTwoD& a, ShapeTwoD& b)
{ 
	return a.getArea() > b.getArea();		
}
//if i only compile this, the compiler is fine with this

void Sort(vector<ShapeTwoD*>& Vector)
{
	string choice;

	cout << "\n\na)\tSort by area (ascending)" << endl;
	cout << "b)\tSort by area (descending)" << endl;
	cout << "c)\tSort by special type and area" << endl;

	cout << "\tPlease select sort option (‘q’ to go main menu): ";
	cin >> choice;
	transform(choice.begin(), choice.end(), choice.begin(), ::tolower);

	if (choice == "a")
	{
		sort(Vector.begin(), Vector.end(), compareAscend);
                //these lines are giving the error
	}
	else if (choice == "b")
	{
		sort(Vector.begin(), Vector.end(), compareDescend);
                //these lines are giving the error
        }
}

But when i try to compile, the compiler will give me A LOAD of errors, which i don't understand.

[Texan40]

You are trying to pass a pointer to ShapeTwoD when compare function is expecting an instance of ShapeTwoD. Either change your Vector to vector<ShapeTwoD> or change your compare function to take pointers to ShapeTwoD instead of references.

[keskiverto]

The vector has objects of some type and the sort passes those objects to the compare.

The same issue (without vector and sort) is seen here:

bool compareAscend( const ShapeTwoD &, const ShapeTwoD & );

int main() {
  ShapeTwoD foo;
  ShapeTwoD bar;
  compareAscend( foo, bar ); // Ok

  ShapeTwoD * pfoo;
  ShapeTwoD * pbar;
  compareAscend( pfoo, pbar ); // Error
}

How about:
bool compareAscend( const ShapeTwoD *, const ShapeTwoD * );

[tokillmob]

Oh, understood, have change and it works now, thanks.