CODEWITHSUNDEEP
ioscore-data
Filip Stefansson
Filip Stefansson

Reputation: 211

CoreData: Add same object multiple times in the To-Many Relationship

Is there any way of adding the same object multiple times i the default CoreData one-to-many relationship?

I have one table with recipes in it, and one table with ingredients.

This is what I'm aiming at:

Apple cake
  - Apple
  - Apple
  - Apple
  - Sugar
  - Flour

Other cake
  - Apple
  - Sugar
  - Flour
  - Flour

By default, the addIngredientsObject-method only adds the ingredient if it doesn't exist in the recipe.

Do I have to create my own table with something like:

Recipe ID
Ingredient ID
Count

or is it possible with the To-Many relationship?

Upvotes: 2

Views: 1506

Answers (1)

Fogmeister
Fogmeister

Reputation: 77621

I'd listen to Matthias with this.

Create a relationship like...

Recipe <->> IngredientMeasure <<-> Ingredient.

i.e. Recipe can have many ingredient measures. Ingredient measure only has one ingredient.

To answer your question though.

In a "to-many" relationship the relationship is mapped to an NSSet. NSSet is a unique collection of objects.

So, if you create an entity called apple and do something like...

[myRecipe addIngredientObject:apple];
[myRecipe addIngredientObject:apple];
[myRecipe addIngredientObject:apple];
[myRecipe addIngredientObject:apple];

You will still end up with only one apple as it is adding the same item to an NSSet which will stop the duplicates.

Upvotes: 3

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