I am relatively new to Swift programming (for ~ 2 months). I have created a simple SwiftData schema made up of the following tables:

ActivityType
Activity
ChallengeGroup
Challenges

@Model
final class ActivityType: Identifiable, Hashable {
    @Attribute(.unique) var activityTypeName: String
    var activityTypeIcon: String
    @Relationship(inverse: Activity.activityType) var activities: [Activity]

@Model
final class Activity: Identifiable, Hashable {
    @Attribute(.unique) var id: Int
    var activityName: String
    @Relationship(inverse: ChallengeGroup.activity) var challengeGroups: [ChallengeGroup]
    var activityType: ActivityType?

@Model
final class ChallengeGroup: Identifiable, Hashable {
    
    @Attribute(.unique) var id: Int
    var challengeGroupName: String
    var category: String
    @Relationship(inverse: Challenge.challengeGroup) var challenges: [Challenge]
    var activity: Activity?

@Model
final class Challenge: Identifiable, Hashable {
    
    @Attribute(.unique) var id: Int
    var challengeName: String
    var challengeGroup: [ChallengeGroup]

I am having a problem trying to obtain all Challenges for a particular Activity.

I have tried declaring within a struct:

    @Query var challenges: [Challenge]

Then within the init():

  init(for activity: Activity) {        
        let id = activity.id 
        self._challenges = Query(filter: #Predicate {
            $0.challengeGroup.activity?.id == id.  <== error here
        }, sort: .challengeName)
        
        self.activity = activity
    }

I am receiving the error of “Value of type ‘[ChallengeGroup]’ has no member ‘activity'” – which makes sense as ChallengeGroup is declared as an array of ChallengeGroups. So if I try:

  init(for activity: Activity) {        
        let id = activity.id 
        self._challenges = Query(filter: #Predicate {
            $0.[challengeGroup].activity?.id == id.  <== error here
        }, sort: .challengeName)
        
        self.activity = activity
    }

I have now added square braces around the name, I receive the error: Expected member name following ‘.’

I am really stuck with this and have no idea how to proceed – it seems like Catch 22. Are you able to provide some solutions to my problem?

Many thanks.