在 Swift (iOS) 和 setValue forKey 中继承 NSObject 的子类

Question

I am writing a base model class which subclasses NSObject, and then each model will be a subclass of this model.

When creating a model I provide a Dictionary<String, AnyObject> of attributes to make up the model properties.

class Model: NSObject {

  var hi: String = "hi"

  init(attributes: Dictionary<String, AnyObject>) {
    super.init()
    for (index, attribute) in attributes {
      self.dynamicType.setValue(attribute, forKey: index)
    }
  }

}

class User: Model {

  var name: String = "Donatello"

}

When I do as below on the direct subclass of NSObject , it works:

let model = Model(attributes: ["hi": "bonjour!"])
print(model.hi) // prints "bonjour!"

and even doing the same on User , the subclass of a class inheriting from NSObject works:

let model = User(attributes: ["hi": "subclass bonjour!"])
print(model.hi) // prints "subclass bonjour!"

but if I try setting properties only available in this subclass, I get the classic this class is not key value coding-compliant for the key name.

for example:

let model = User(attributes: ["name": "Raphael"])

causes error.

Why does this error occur when this object, as a subclass of a class inheriting from NSObject, should inherit from NSObject automatically.

Is this a problem with my fundamental understanding of subclassing?

Answer 1

The problem is with your understanding of something much more basic: classes and instances. Change:

  self.dynamicType.setValue(attribute, forKey: index)

to:

  self.setValue(attribute, forKey: index)