领域 - 返回数组列表

Question

我有一个名为mood的领域对象，我试图将字段活动中的所有值作为[String]列表返回，其中mood = great

我的Realm对象看起来像：

Results<Mood> <0x7fce164851a0> (
    [0] Mood {
        mood = Great;
        comment = test;
        activities = Friends;
        time = 8:06 PM;
        date = 4/10/18;
        symptom = down;
    },
    [1] Mood {
        mood = Sad;
        comment = ;
        activities = Date;
        time = 6:22 PM;
        date = 4/14/18;
        symptom = up;
    },
    [2] Mood {
        mood = Sad;
        comment = ;
        activities = Date;
        time = 7:40 PM;
        date = 4/14/18;
        symptom = Night;
    },
    [3] Mood {
        mood = Sad;
        comment = ;
        activities = Date;
        time = 7:41 PM;
        date = 4/14/18;
        symptom = Dry;
    },
    [4] Mood {
        mood = Awful;
        comment = this is an example data for the app!;
        activities = Date;
        time = 2:17 PM;
        date = 4/15/18;
        symptom = Lost;
    }
)

我想返回一个像这样的列表

[“down”]因为那是心情=伟大的活动等

我试过了：

func getGreatMoodActivity() -> [String]{
    let greaMoodActivity = Set(realm.objects(Mood.self).filter("mood = 'Great'") as! [String])
    return getGreatMoodActivity()
}

但是这个错误会崩溃

无法将'RealmSwift.Results'（0x10f520810）类型的值转换为'NSArray'（0x10ce35008）。

有没有办法来解决这个问题？

Answer 1

filter操作将继续过滤符合您给定标准的Mood对象，因此其返回值将为Results<Mood>类型，您显然无法将其强制转换为Array<String>。

看来你实际上是在尝试map匹配你的过滤条件的Mood对象到它们的symptom属性String属性。为了实现您的目标，您需要在过滤map对象后调用Mood。

此外，您的返回值是完全有缺陷的，您希望返回存储在变量greatMoodActivity中的数组，而不是递归调用您的函数。

func getGreatMoodActivity() -> [String]{
    let greatMoodActivity = realm.objects(Mood.self).filter("mood = 'Great'").map({$0.symptom})
    return Array(greatMoodActivity)
}