SwiftData - Problems with Predicates and Relations

Question

Fachwerk OP

Created Oct ’24

Replies 3

Boosts 0

Participants 2

Hello,

I have a problem with SwiftData and Predicates that check for the persistentModelID of the relations.

My data model looks simplified like this:

Day -> TimeEntry[] -> Hashtag[]

What I want to achieve is to query the days and associated time entries via assigned tags.

This is my predicate:

       let identifier = filterHashtags.map(\.persistentModelID)
       ...
       #Predicate<TimeEntry> { timeEntry in
            identifiers.count == timeEntry.tags.filter { tag in
                identifiers.contains(tag.persistentModelID)
            }.count
        }

It does not return any data when I check for the persistentModelID. However, if I use another property of the tags, e.g. the name or a generated UUID for the check, the predicate works. Is this a general problem with PersistentIdentifier in Predicates or am I missing something?

Thanks in advance

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Answer 1

joadan OP

Oct ’24

where does the content of filterHashtags come from?

0

Answer 2

Fachwerk OP

Oct ’24

The hashtags come from my HashtagFilter model and are attached there as a relationship.

    @Model
    final class HashtagFilter: Identifiable, Hashable, NamedEntity {
        @Relationship(inverse: \Hashtag.hashtagFilter)
        var tags: [Hashtag]
        var displayName: String
        
        @Relationship(deleteRule: .cascade, inverse: \HashtagFilter.parentItem)
        var children: [HashtagFilter]?
        var parentItem: HashtagFilter?
                
        @Transient
        var isEditing: Bool = false
        
        init(displayName: String) {
            self.tags = []
            self.children = []
            self.displayName = displayName
        }
    }
    ```

The filterHashtags come from HashtagFilter.tags. If I check for equality in my code, it works. It just doesn't work in the Predicate. However, due to the amount of data, I would like to perform this filtering in the Predicate

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Answer 3

joadan OP

4w

~~But Hashtag and HashtagFilter are two different models so why should their persistentModelID values be equal?~~ Your variable naming confused me.

0