Question

我有一个领域：

class Train: RLMObject {
    dynamic var stationDeparture: Station?
    dynamic var trainId = 0
    dynamic var route = RLMArray(objectClassName: Route.className())
    override class func primaryKey() -> String {
        return "trainId"
    }
}
class Route: RLMObject {
    dynamic var numberInRoute = 0
    dynamic var station: Station?
    var owners: [Train] {
        return linkingObjectsOfClass("Train", forProperty: "Route") as! [Train]
    }
}
class Station: RLMObject {
    dynamic var code = 0
    dynamic var name = ""
    override class func primaryKey() -> String {
        return "code"
    }
    dynamic var relatedStations = RLMArray(objectClassName: Station.className())
}

我试图在[{1}} class Train: RLMObject为dynamic var stationDeparture: Station?获取车站和车站相关车站的所有列车。起初我从相关站的代码中创建了一个字符串，然后在谓词中使用“IN”进行查询。

这个功能很有用，很难看但是有效！：

func trainsForDepartureStation (station: Int) -> RLMResults? {
    let stations = Station.objectsWhere("code == \(station)")
    let related = stations.lastObject() as! Station
    if related.relatedStations.count > 0 {
        var st = ""
        st += "{\(station)"
        for id in 0...related.relatedStations.count-1 {
            st += ", \(related.relatedStations[id].code)"
        }
        st += "}"
        let trains = Train.objectsWhere("stationDeparture.code IN \(st)")

        return trains

    } else {
        let trains = Train.objectsWhere("stationDeparture.code == \(station)")
        return trains
    }
}

但是当我试图在火车的所有路线上使用所有车站的火车时，它也不起作用。

let trains = Train.objectsWhere("ANY route.station.relatedStations.code IN \(st)")

错误是：

'Invalid predicate', reason: 'Predicate with ANY modifier must compare a KeyPath with RLMArray with a value'

如何针对此问题进行嵌套查询？我是快速的，客观的 - с和领域（

Answer 1

您可能已经猜到，您必须将该查询分解为多个查询。首先，让我们重构trainsForDepartureStation()以更好地了解它目前在做什么：

func trainsForDepartureStation(station: Int) -> RLMResults? {
  let stations = Station.objectsWhere("code == \(station)")
  if let related = stations.lastObject() as? Station where related.relatedStations.count > 0 {
    return Train.objectsWhere("stationDeparture IN %@", related.relatedStations)
  } else {
    return Train.objectsWhere("stationDeparture.code == \(station)")
  }
}

好的，现在让我们改变一下，返回“列车所有列车所有车站的列车”：

func trainsForDepartureStation(station: Int) -> RLMResults? {
  let stations = Station.objectsWhere("code == \(station)")
  if let related = stations.lastObject() as? Station where related.relatedStations.count > 0 {
    let allRelatedStations = Station.objectsWhere("relatedStations IN %@", related.relatedStations)
    let allRelatedRoutes = Route.objectsWhere("station IN %@", allRelatedStations)
    return Train.objectsWhere("ANY route IN %@", allRelatedRoutes)
  } else {
    let allRelatedRoutes = Route.objectsWhere("station == %@", stations.lastObject() as! Station)
    return Train.objectsWhere("ANY route IN %@", allRelatedRoutes)
  }
}

Answer 2

只有一个错误，这一部分：

    let allRelatedStations = Station.objectsWhere("relatedStations IN %@", related.relatedStations)
    let allRelatedRoutes = Route.objectsWhere("station IN %@", allRelatedStations)

应替换为：

    let allRelatedRoutes = Route.objectsWhere("station IN %@", related.relatedStations)

因为allRelatedStations没有获取相关的站点，而只是再次获取父站点

如何在Realm

2 个答案: