iOS Realm Filter objects in a list of a relationship

Question

I have three objects nested via lists like this:

class Canteen: Object {

        dynamic var name: String?
        let lines = List()
}

class L         


        

Answer 1

Realm allows it to use functions as parameter for the filtering. So this is my solution which im currently using.

The two filter functions:

func vegetarianFilter(_ meal: Meal) -> Bool {

        if showVegetarianOnly {
            if(meal.veg || meal.vegan){
                return true
            }

            return false
        }

        return true
}

func filterEmptyLines(_ line: Line) -> Bool {

       if(line.meals.filter(vegetarianFilter).count > 0){
           return true
       }

       return false
}

The functions filter all meals which are not vegetarian or vegan when the user has selected showVegetarianOnly = true. Also it filters all lines which than have no meal left (nothing is vegetarian or vegan).

Most important functions of the TableView:

    override func numberOfSections(in tableView: UITableView) -> Int {
            return canteenDay?.lines.filter(filterEmptyLines).count ?? 0
    }

    override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
            return canteenDay?.lines.filter(filterEmptyLines)[section].meals.filter(vegetarianFilter).count ?? 0
    }

   override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {

        let cell = UITableViewCell()

        let meal = canteenDay!.lines.filter(filterEmptyLines)[indexPath.section].meals.filter(vegetarianFilter)[indexPath.row]

        cell.textLabel?.text = meal.meal

       return cell
    }