核心数据：在实体ZZZZ上找不到属性YYYY的类名称为XXX的NSValueTransformer [英] Core Data : No NSValueTransformer with class name XXX was found for attribute YYYY on entity ZZZZ

问题描述

我在xcdatamodel文件中设置了CoreData模型。

I have my CoreData model set in a xcdatamodel file.

我的属性YYYY具有可转换的类型，我在数据模型检查器中设置了转换器名称。

My attribute YYYY has a type transformable and I set the tranformer name in the Data model inspector.

我的情况是我在模型中存储了 [CLLocation] 。

I my case I was storing a [CLLocation] in my model.

class LocationArrayTransformer : NSValueTransformer {


    override func transformedValue(value: AnyObject?) -> AnyObject? {

        let locations = value as! [CLLocation]

        return NSKeyedArchiver.archivedDataWithRootObject(locations)
    }

    override func reverseTransformedValue(value: AnyObject?) -> AnyObject? {

        let data = value as! NSData

        return NSKeyedUnarchiver.unarchiveObjectWithData(data)
    }


}

那是我的价值转换器。

That's my value transformer.

但是我仍然会在控制台中收到警告：在实体ZZZZ上没有为属性YYYY找到类名称为XXX的NSValueTransformer

But somehow I'm still getting the warning in the console : No NSValueTransformer with class name XXX was found for attribute YYYY on entity ZZZZ

任何想法为何？

推荐答案

我花了很多时间在此上，以不分享我发现的解决方案：

I spent way to much time on this to not share the solution I found :

我必须将 NSValueTransformer 子类提供给Objc。

I had to make the NSValueTransformer subclass available to Objc.

@objc(LocationArrayTransformer)
class LocationArrayTransformer : NSValueTransformer {
 ....
}

就这么简单。

@Sbooth指出，Swift类具有名称空间。使用 @objc 可使类可用而无需命名间隔。因此，将转换器名称设置为 MyApp.Mytransformer 也可以！

As @Sbooth points out, Swift classes are namespaced. Using @objc makes the class available without namespacing. So setting the transformer name as MyApp.Mytransformer works well too !

这篇关于核心数据：在实体ZZZZ上找不到属性YYYY的类名称为XXX的NSValueTransformer的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！