"String Iterators Incompatible" error message when running bubble sort program

Question

I am a beginner trying to bubble sort a vector of objects in C++. My goal is to sort the vector by member variables of each object element's member variable. So in the end, I would like the attributes off all the vector elements to be the same, just sorted in a different order. When I run the program, I get the following message:

Here is my code:

    void sortInventory(vector<Vehicle> &carList)
    {
    bool swap;      
    Vehicle temp;  

    do
    {
        swap = false;

        for (int count = 0; count < carList.size(); count++)
        {

            transform(carList[count].getVIN().begin(), carList[count].getVIN().end(), carList[count].getVIN().begin(), ::tolower);

            if (carList[count].getVIN() > carList[count + 1].getVIN())
            {
                temp = carList[count];                          
                carList[count] = carList[count + 1];
                carList[count + 1] = temp;
                swap = true;    
            }
        }

    } while (swap);
}

Here is my class declaration:

class Vehicle
{
private:
    string VIN;

public:
    string getVIN();
    void   setVIN(string);

};

Here is my class implementation:

string Vehicle::getVIN()
{   return VIN;     }

void Vehicle::setVIN(string input)
{   VIN = input;    }

By the way, I am aware that I am not using efficient methods, but I am just starting to learn the language and I am learning to write the code.

I asked a question similar to this here. However, none of the answers got me to where I wanted to go, although I feel like I am going in the right direction.

Answer 1

As jxh says, your transform line fails because you are making iterators to separate string objects. Why not try making the transform a separate routine? If you want to be fancy you can define it inside the sort routine as a lambda function. Or you can just make it a separate routine defined separately.

// returns a lower case version of the string
std::string lower_case(std::string VIN_number){

  auto begin = std::begin(VIN_number);
  auto end = std::end(VIN_number);

  // Your code acting on one fixed string
  std::transform(begin, end, begin, ::tolower);

  return VIN_number; 
 }

Then when you do your comparison, do something like

if ( lower_case(carList[count].getVIN()) > lower_case(carList[count + 1]).getVIN()) )