Currently we have a database of multiple values for r,g,b, split into own attributes. ex:
r = type float
g = type float
b = type float
There will be multiple values for each r, g, and b attribute. After getting a float from an outside source, we want to search the database to return the attribute with the closest number to that float. (ex. for r, if we get a value of 199, the r value with the closest value to 199 will be returned).
I know there are predicates that can be used like: "text CONTAINS[c] %@" but I didn't see any predicates for 'closest value'.
You can use NSSortDescriptor(key: "name_key", ascending: true) with your request.
let request1 = NSFetchRequest<NSFetchRequestResult>() // use correct constructor
let sortDescriptor = NSSortDescriptor(key: "name_key", ascending: true)
let sortDescriptors = [sortDescriptor]
request1.sortDescriptors = sortDescriptors
let predicate1 = NSPredicate(format: "text < %@", value)
request1.predicate = predicate1
// use this request1 to fetch from core data
let request2 = NSFetchRequest<NSFetchRequestResult>() // use correct constructor
request2.sortDescriptors = sortDescriptors
let predicate2 = NSPredicate(format: "text > %@", value)
request2.predicate = predicate2
// use this requst2 to fetch from core data
Then you can use predicate twice:
First time with format text < %@ and use last item of the array.
and
Second time with format text > %@ and use the first item of the array.
compare the difference of your first and last items from both iterations with your given value and see whose difference is smaller. That will be closest value.
If you don't know how to fetch data from core data you can follow Fetching Objects