根据日期和链接数据过滤 fetchRequest答案

【问题标题】：Filter fetchRequest based on date and linked data根据日期和链接数据过滤 fetchRequest
【发布时间】：2021-09-28 13:44:34
【问题描述】：

我在 CoreData 中有 2 个数据表

锻炼：

extension Workout {

    @nonobjc public class func fetchRequest() -> NSFetchRequest<Workout> {
        return NSFetchRequest<Workout>(entityName: "Workout")
    }

    @NSManaged public var id: UUID?
    @NSManaged public var name: String?
    @NSManaged public var type: String?
    @NSManaged public var notes: String?
    @NSManaged public var created_at: Date?
    @NSManaged public var updated_at: Date?
    @NSManaged public var sessions: NSSet?
    @NSManaged public var pinned: Bool
}

会话：

extension WorkoutSession {

    @nonobjc public class func fetchRequest() -> NSFetchRequest<WorkoutSession> {
        return NSFetchRequest<WorkoutSession>(entityName: "WorkoutSession")
    }

    @NSManaged public var created_at: Date?
    @NSManaged public var id: UUID?
    @NSManaged public var reps: Int16
    @NSManaged public var sets: Int16
    @NSManaged public var duration: Int64
    @NSManaged public var updated_at: Date?
    @NSManaged public var measurement: Double
    @NSManaged public var notes: String?
    @NSManaged public var type: Workout?
}

我想创建一个获取请求，以获取在某一天有会话的所有锻炼。

我现在要做的是单独获取所有的锻炼和课程。让用户选择一个日期。根据该日期过滤所有会话，映射会话以返回锻炼并使该数组独一无二。哪个可行，但我想可能会更好。


@FetchRequest(entity: Workout.entity(), sortDescriptors: [NSSortDescriptor(key: "name", ascending: true)]) var fetchedWorkouts: FetchedResults<Workout>
@FetchRequest(entity: WorkoutSession.entity(), sortDescriptors: [NSSortDescriptor(key: "created_at", ascending: true)]) var sessions: FetchedResults<WorkoutSession>

@State private var day = Date()

var filteredList: [WorkoutSession] {
    return sessions.filter { session in
        Calendar.current.isDate(session.created_at ?? Date(), inSameDayAs:day)
    }
}

var filteredWorkouts: [Workout] {
    let sessionsWithType = filteredList.filter { session in
        return session.type != nil
    }
    let uniqueWorkouts = Array(Set(sessionsWithType.map { session in
        return session.type!
    }))
    return uniqueWorkouts.sorted { workoutA, workoutB in
        return workoutA.wrappedName < workoutB.wrappedName
    }
}

我最终想要实现的是用户可以选择一天的视图。然后，该应用程序将显示一个列表视图，该视图分为每个锻炼的部分，在这些部分中，您将看到您当天为该锻炼所做的会话。

例如：这些部分是单独的视图，用于获取所选日期的特定锻炼的会话。所以在这个主视图上，我只想要当天有课程的锻炼。

请让我知道您需要更多数据

【问题讨论】：

developer.apple.com/wwdc21/10017

标签： swift core-data swiftui

【解决方案1】：

        self.date = date
        
        var calendar = Calendar.current
        calendar.timeZone = NSTimeZone.local
        let startOfDay = calendar.startOfDay(for: date)
        let endOfDay = calendar.date(byAdding: .day, value: 1, to: startOfDay)!
        
        let workoutPredicate = NSPredicate(format: "SUBQUERY(sessions, $s, $s.created_at >= %@ AND $s.created_at < %@).@count > 0", argumentArray: [startOfDay,endOfDay])
        self.workoutRequest = FetchRequest<Workout>(
            entity: Workout.entity(),
            sortDescriptors: [
                NSSortDescriptor(key: "created_at", ascending: true)
            ],
            predicate: workoutPredicate
        )

【讨论】：