核心数据在一对多关系查询中

Question

我有一个像这样的核心数据对象：

我建立一个谓词，以获得我需要获得电影和剧院的预定时间和每个选择时间

随着时间表的价值我试图去剧院

这是我的代码：

 NSString *nameOfMovie = [[scheduleResults movie] valueForKey:@"nameOfMovie"];

NSPredicate *theaterPredicate  = [NSPredicate predicateWithFormat:@"SUBQUERY (showTimes, $x, $x.nameOfMovie == %@ AND $x.showTimes.showTimes == %@).@count > 0", nameOfMovie, showTimes];

但是我的谓词出现了这个错误：

这里不允许使用多个键

你们中的任何人都知道我的谓词出错了吗？

Answer 1

我发现这个问题非常有趣，所以创建一个简单的游乐场，用swift来测试你的案例的子查询。我认为你错过了数据模型中的某些关系，如果你真的关心它，你应该用单数命名实体，如电影，日程表，剧院等更有意义，因为实体总是单一的，关联可以是单数或复数取决于一对多或一对一的关系。

以下是我提出的数据模型，

// a Movie can have multiple schedule and a schedule can have multiple movies at the same time
Schedule << -------  >> Movie

// a Movie can be running in multiple theater and a theater can have multiple movies
Movie << ------>> Theater

因此，基于上述关系，我创建了一个操场文件来创建一些夹具数据并进行游戏，

class Schedule: NSObject {
    var showTime: NSDate!
    var movies: [Movie]!
}

class Theater: NSObject {
    var name: String!
    var movies: [Movie]!
}

class Movie: NSObject {
    var nameOfMovie: String!
    var theaters: [Theater]!
    var showTimes: [Schedule]!
}

let hitech = Theater()
hitech.name = "Hitech Cinema"

let kino = Theater()
kino.name = "Kino"

let warner = Theater()
warner.name = "Warners"


let interstellar = Movie()
interstellar.nameOfMovie = "Interstellar"

let gravity = Movie()
gravity.nameOfMovie = "Gravity"

let wrathOfSpace = Movie()
wrathOfSpace.nameOfMovie = "Wrath of Space"

let today = NSDate()
let yesterday = today.dateByAddingTimeInterval(-60 * 60 * 24)
let tomorrow = today.dateByAddingTimeInterval(60 * 60 * 24)


let todaySchedule = Schedule()
todaySchedule.showTime = today

let yesterdaySchedule = Schedule()
yesterdaySchedule.showTime = yesterday

let tomorrowSchedule = Schedule()
tomorrowSchedule.showTime = tomorrow


todaySchedule.movies = [interstellar, gravity]
tomorrowSchedule.movies = [interstellar, wrathOfSpace]
yesterdaySchedule.movies = [wrathOfSpace, gravity]

interstellar.showTimes = [todaySchedule, tomorrowSchedule]
gravity.showTimes = [todaySchedule, yesterdaySchedule]
wrathOfSpace.showTimes = [tomorrowSchedule, yesterdaySchedule]

interstellar.theaters = [kino, hitech]
gravity.theaters = [kino, warner]
wrathOfSpace.theaters = [warner, hitech]

kino.movies = [interstellar, gravity]
hitech.movies = [interstellar, wrathOfSpace]
warner.movies = [wrathOfSpace, gravity]


let theaters:NSArray = [hitech, warner, kino]


var nameOfMovie = "Gravity"
var date = yesterday

var predicate = NSPredicate(format: "SUBQUERY(movies, $a, $a.nameOfMovie = %@ and SUBQUERY($a.showTimes, $b, $b.showTime = %@).@count > 0).@count > 0", nameOfMovie, date)

let threatersYesterdayGravity = theaters.filteredArrayUsingPredicate(predicate)


nameOfMovie = "Interstellar"
date = tomorrow

predicate = NSPredicate(format: "SUBQUERY(movies, $a, $a.nameOfMovie = %@ and SUBQUERY($a.showTimes, $b, $b.showTime = %@).@count > 0).@count > 0", nameOfMovie, date)

let threatersTomorrowInterstellar = theaters.filteredArrayUsingPredicate(predicate)

结果如我所料。您还可以使用上述关系，子查询符合您的需要。