Btukfyl

I have one to many relationship between two models, Product and WishList like the code below

class Product : Object {



    @objc dynamic var productID : String = ""

    @objc dynamic var name : String = ""

    @objc dynamic var unitPrice: Double = 0.0

    @objc dynamic var imagePath : String = ""

    @objc dynamic var quantity = 0

    @objc dynamic var hasBeenAddedToWishList : Bool = false

    var parentCategory = LinkingObjects(fromType: WishList.self, property: "products")



    convenience init(productID : String, name: String, unitPrice: Double, imagePath: String, quantity: Int = 1, hasBeenAddedToWishList: Bool = false) {

        self.init()



        self.productID = productID

        self.name = name

        self.unitPrice = unitPrice

        self.imagePath = imagePath

        self.quantity = quantity

        self.hasBeenAddedToWishList = hasBeenAddedToWishList

    }



    override static func primaryKey() -> String? {

        return "productID"

    }



}

and WishList:

class WishList : Object {

    @objc dynamic var userID: String = ""

    var products = List<Product>()

}

I try to add or remove product to WishList using the code below when love button in the image above is pressed :

    // 1. get the wishlist based on UserID



    let allWishList = realm.objects(WishList.self)

    let theWishList = allWishList.filter("userID CONTAINS[cd] %@", userID).first



    guard let userWishList = theWishList else {return}





    // 2. modify Wishlist data in Realm.



    if loveIconHasBeenFilled {



       guard let index = userWishList.products.index(where: {$0.productID == selectedProduct.productID}) else {return}



       do {

        // remove data from realm database            



          try realm.write {

            userWishList.products.remove(at: index)

          }



        } catch {

          // error Handling

        }







    } else {



      do {



         // add product to wishlist model in realm database



         try realm.write {

            userWishList.products.append(selectedProduct)

         }



      } catch {

        // error Handling

      }





   }

and here is the data in Realm Browser

and the problem is ....

when I run the app for the first time, I can add, and then remove, and then add the product again to the wishlist, and the number of product in the realm database still be the same (all have unique productID)

but when I restart the app, and try to click that love button to add the product to wishlist again, it throws an error

'RLMException', reason: 'Attempting to create an object of type
'Product' with an existing primary key value 'a'

this error is triggered because of this line of code userWishList.products.append(selectedProduct) , when adding the product to WishList, it automatically adds Product in the realm database. so because I keep adding the same product that has the same productID (primary key) it will throw that error.

so, my question is, how to avoid addition in Product if it has the same productID (primary key), it is better if i can just update the product in realm database when adding the product to the wishlist using this line of code: userWishList.products.append(selectedProduct)

You could check the property hasBeenAddedToWishList of the selected product and only add it if the property is false.

 if loveIconHasBeenFilled {

   //your logic to remove already added products



} else if !selectedProduct.hasBeenAddedToWishList { //<--- check if the product already exists in wishlist if not you add it



  do {



     // add product to wishlist model in realm database



     try realm.write {

        userWishList.products.append(selectedProduct)

     }



  } catch {

    // error Handling

  }

}