If I understand you correctly, as vaibhav implied your question seems pretty general and probably relates more to structuring your data to fit your requirements than to technical aspects of the iOS / CoreData environment. In that vein, I’ll offer a few thoughts I’d have in structuring a data structure for quality ratings per your description.
If your ratings will always be for the three categories you show, i.e. Quality, Value and Price, I wouldn’t over-complicate things; I’d just use three properties in a rating record to hold the values that a user assigns in his/her rating of a product (just showing selected attributes and relationships in all following lists):
Product
name
Rating
ratedProduct (many to one)
qualityRating Int
valueRating Int
priceRating Int
Done this way you’d need to associate the values with their types in code for the APIs, such as (where item is a retrieved rating record):
display(product: item.ratedProduct.name, quality: item.qualityRating, value: item.valueRating, price: item.priceRating).
On the other hand, you may be describing a more generic approach that would allow for ratings categories that vary more frequently, or perhaps vary among products. This could apply where, for example, ratings include how well things fit for clothing but not for other products like books. In that case, you’d need a more complicated structure where a product could have a variable number of ratings of different types, so you’d need another layer of entities that let you create an arbitrary number of rating records that applied to a product.
Here you'd create a separate rating record for each rating that a user assigned to a product.
The simplest form of that structure would be like the following:
Product
name String
UserEvaluation
ratedProduct (many to one)
productRating (one to many)
ProductRating
ratingType (many to one)
value Int
RatingType
ratingTitle String
ratingID String or Int
Then you’d have to have a bit more structure where you'd list the product and then access the ratings with a loop that cycled through the set of all of the ratings linked to the product record somewhat like this (where item is a retrieved UserEvaluation):
displayTitle(product: item.ratedProduct.name)
for rating in item.productRating {
displayRating(ratingTitle: item.productRating.ratingType.title, ratingValue: item.productRating.value)
}
You'd probably want to combine these into a method that takes the name and an array of ratings.
To keep track of things, you’d also probably want to create another entity that defined product classes and specified what specialized ratings applied to each class (like fit for clothing and mileage for cars). By default, you also may want to allow for a few generic rating types that apply to all products (like the quality and price ratings you show). For this approach, the full structure would look like this:
Product Category
title
ratingType (many to many)
Product
productType (many to one)
UserEvaluation
ratedProduct (many to one)
productRating (one to many)
ProductRating
ratingType (many to one)
value Int
RatingType
ratingTitle String
ratingID String or Int
With this structure, once a product is assigned a productType, the application would know what ratings to ask for in the UI.
You could try building more complicated rating records with all of the types that apply to a product category, but that would get very messy if the applicable categories vary over time. You could also create a "custom" rating type that let a user specify a title and input a rating, in which case you'd need a text field in the rating record that only applies if the ratingType is "custom".
I hope this helps…
