Where should I put contextual data related to an Object that is not really a property of the object?

Question

I have a Car class. It has three properties: id, color and model.

In a particular query I want to return all the cars and their properties, and I also want to return a true/false field called "searcherKnowsOwner" which is a field I calculate in my database query based on whether or not the individual conducting the search knows the owner. I have a database function that takes the ID of the searcher and the ID of the car and returns a boolean.

My car class looks like this (pseudocode):

class Car{
  int id;
  Color color;
  Model model;
}

I have a screen where I want to display all the cars, but I also want to display a flag next to each car if the person viewing the page knows the owner of that car.

Should I add a field to the Car class, a boolean searcherKnowsOwner? It's not a property of the car, but is actually a property of the user conducting the search. But this seems like the most efficient place to put this information.

Answer 1

I would model it this way:

class Car{
  int id;
  Color color;
  Model model;
  Owner owner;
}

class Owner {
  Boolean knowsSearcher;
}

Now the Car type has an Owner (a bit backwards from real life, yes) and the Owner type has a field indicating whether or not they know the searcher.

Answer 2

Let the Car and Owner object remain unchanged. Define 2 classes SearchCriteria and SearchResults

SerachCriteria will hold the search criteria as supplied by end-user and your application logic will return an object of type SearchResults that is a collection of Cars.

You can maintain a flag within SearchResult corresponding to each car object in the result for if the owner is known.