Swift：反映NSManagedObject子类的属性 [英] Swift: Reflecting properties of subclass of NSManagedObject

问题描述

使用镜像访问NSManagedObject子类的内部结构时，将忽略所有托管变量。

When accessing the inner structure of a subclass of NSManagedObject using a Mirror, all managed variables are ignored.

public class Foo: NSManagedObject {
   @NSManaged var bar: String?
}

var f: Foo = ...
// ... creating a Foo in a valid context ...

let mirror = Mirror(reflecting: f)
for c in mirror.children {        // children count == 0
  print("\(c.label!):\(c.value)") // never executed
}

如何在NSManagedObjects上使用反射机制。

How can reflection mechanisms used on NSManagedObjects.

推荐答案

Core Data属性的访问器方法在运行时动态地合成
。

The accessor methods for Core Data properties are synthesized dynamically at runtime.

您可以使用
的 NSManagedObject 的实体属性来枚举Core Data实体的属性。是 NSEntityDescription
并具有 attributesByName 属性。

You can enumerate the attributes of a Core Data entity using the entity property of NSManagedObject which is a NSEntityDescription and has a attributesByName property.

一个简单的示例：

for (name, attr) in  newManagedObject.entity.attributesByName {
    let attrType = attr.attributeType // NSAttributeType enumeration for the property type
    let attrClass = attr.attributeValueClassName ?? "unknown"
    print(name, "=", newManagedObject.valueForKey(name), "type =", attrClass)
}

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