I have a CoreData-Entity that stores an attribute called "imageUrl" of type "URI". It's used to store URL's (as in Swift URL / NSURL) for eg. rendering remote images.
How would I query for the string representation of an URI-type attribute?
Example: I'd like to get all objects that match "http://mydomain.jpg" or URL(string: "http://mydomain.jpg") to be more precise.
For attributes that are "String"-typed this would be sufficient:
NSPredicate(format: "myStringAttribute LIKE %@", "http://mydomain.jpg")
Would the following work for URI-type attributes?
NSPredicate(format: "imageUrl LIKE %@", URL(string: "http://mydomain.jpg"))
I'm answering to not let that question without an answer, but in my opinion, we three @nylki (the author), @Joakim Danielson and myself answered it together. I'll mark it as "Community Wiki" then.
URI in CoreData is a for URL objects. It's written as such in the documentation of NSAttributeDescription.AttributeType for the NSAttributeDescription.AttributeType.uri.
LIKE keyword in the predicate is for String comparison as stated by the Predicate Format String Syntax documentation, so we need to use = instead.
So the answer is:
NSPredicate(format: "imageUrl = %@", imageUrl as CVarArg)
Or
NSPredicate(format: "imageUrl = %@", argumentArray: [imageUrl])
if we don't want to use the as CVarArg.
A better way to avoid typo would be to use %K placeholder which is for %K is a var arg substitution for a key path.. Combined to #keyPath():
NSPredicate(format: "%K = %@", argumentArray: [#keyPath(YourEntityClass.imageUrl), imageUrl])
That way, if we wrote by error "imageUrI = %@" with an uppercase i instead of l that with might not see, we ensure the path.