ios - Realm - 返回数组列表

Question

我有一个名为心情的 Realm 对象，我试图将字段事件中的所有值作为 [String] 列表返回，其中心情 = 很棒

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

[“向下”] 因为这就是心情=很棒等的事件

我已经尝试过:

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

但是这个错误导致崩溃

Could not cast value of type 'RealmSwift.Results' (0x10f520810) to 'NSArray' (0x10ce35008).

有办法解决这个问题吗？

Answer 1

filter操作将保持过滤 Mood与给定条件匹配的对象，因此其返回值的类型为 Results<Mood>显然你不能强制转换为 Array<String> 。

看来您实际上是在尝试map Mood与您的过滤条件匹配的对象 symptom属性，其类型为 String 。为了实现您的目标，您需要调用map过滤 Mood 后对象。

而且，你的返回值完全有缺陷，你想返回变量greatMoodActivity中存储的数组并且不递归调用您的函数。

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