领域 - 返回数组列表

Question

我有一个名为 mood 的领域对象，我正在尝试将字段活动中的所有值作为 [String] 列表返回，其中 mood = great

我的 Realm 对象如下所示：

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;
    }
)

我想返回一个类似

的列表

[“向下”] 因为那是心情=很棒等的活动

我试过了：

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

但是这会因为这个错误而崩溃

无法转换“RealmSwift.Results”类型的值 (0x10f520810) 到 'NSArray' (0x10ce35008)。

有没有办法解决这个问题？

Answer 1

filter 操作将继续过滤符合您给定条件的Mood 对象，因此其返回值将是Results<Mood> 类型，您显然无法强制转换为Array<String>。

看来您实际上是在尝试map Mood 对象匹配您的过滤条件到它们的symptom 属性，该属性是String 类型。为了实现您的目标，您需要在过滤完Mood 对象后调用map。

此外，您的返回值完全有缺陷，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)
}