如何在 Swift 中的 Realm.io 中做抽象实体

Posted 2023-03-11

【中文标题】如何在 Swift 中的 Realm.io 中做抽象实体

【英文标题】：How to do Abstract Entities in Realm.io in Swift

【发布时间】：2015-04-23 19:48:47

【问题描述】：

我正在从 CoreData 转换到 Realm.io 我做了一个小实验来看看 Realm.io 如何处理我需要有一个 RLMObject 类的子类的情况。

型号

import Realm

@objc enum RecurrenceEnum : Int 
    case Daily = 1
    case Weekly = 2
    case Monthly = 3


class Challenge: RLMObject 
    dynamic var title = ""


class TotalCountChallenge: Challenge 
    dynamic var totalCountGoal: Int = 0


class RecurringChallenge: Challenge 
    dynamic var recurranceType: RecurrenceEnum = .Daily
    dynamic var totalCountGoal: Int = 0

当我保存 TotalCountChallenge 或 A RecurringChallenge 时，它​​不会报告任何错误，但是当我按标题查询挑战时，我什么也得不到。

从我的 ViewController 查询

// Query using an NSPredicate object
let predicate = NSPredicate(format: "title BEGINSWITH %@", "Booya")
var challenges = Challenge.objectsWithPredicate(predicate)

if challenges == nil || challenges.count == 0 
    let tcChallenge = TotalCountChallenge()
    tcChallenge.title = "Booya Total Count Challenge"
    tcChallenge.totalCountGoal = 1_000_000

    let rChallenge = RecurringChallenge()
    rChallenge.title = "Booya Recurring Challenge"
    rChallenge.recurranceType = .Weekly
    rChallenge.totalCountGoal = 2_000_000

    let realm = RLMRealm.defaultRealm()
    // You only need to do this once (per thread)

    // Add to the Realm inside a transaction
    realm.beginWriteTransaction()
    realm.addObject(tcChallenge)
    realm.addObject(rChallenge)
    realm.commitWriteTransaction()


challenges = Challenge.objectsWithPredicate(predicate)
if challenges != nil && challenges.count > 0 
    for challenge in challenges 
        let c = challenge as! Challenge
        println("\(c.title)")
    
 else 
    println("No Challenges found")


challenges = TotalCountChallenge.objectsWithPredicate(predicate)
if challenges != nil && challenges.count > 0 
    for challenge in challenges 
        let c = challenge as! Challenge
        println("TotalCountChallenge: \(c.title)")
    
 else 
    println("No Total Count Challenges found")


challenges = RecurringChallenge.objectsWithPredicate(predicate)
if challenges != nil && challenges.count > 0 
    for challenge in challenges 
        let c = challenge as! Challenge
        println("RecurringChallenge \(c.title)")
    
 else 
    println("No Recurring Challenges found")

输出

No Challenges found
TotalCountChallenge: Booya Total Count Challenge
RecurringChallenge Booya Recurring Challenge

当我使用 Realm 提供的浏览工具查看数据库时，我发现只有 1 个 TotalCountChallenge 和 1 个 RecurringChallenge，并且没有任何挑战

有没有办法做到这一点？

这里是github中的代码链接：lewissk/RealmTest

【参考方案1】：

Realm 支持子类化，但不支持您正在寻找的那种多态性。在 Realm 中，每个对象类型都存储在自己的表中，无论您是否在代码中将其声明为另一个对象的子类。这意味着目前不可能跨不同的对象类进行查询，即使它们共享一个公共超类。在 https://github.com/realm/realm-cocoa/issues/1109 跟踪此功能请求时出现问题。