Objective-C：领域中对象的部分更新

Question

The problem: I'm using Realm along the AFNetworking library. To keep things clean I'm working with custom serializers parsing incoming json responses and mapping them to objects. The returned objects a than saved, updated or in some cases forwarded. The problem is that some relations get overwritten and I need to execute a kind of partial update.

Is there a way in realm to copy a persisted object and add its values to a non-persisted object, updated with response values only?

Example:

Current state:

cat{
   name: "kitty"
   owners: ["peter"] 
}

Incoming Response:

cat{
    name:"pussy"
    owner:[]
}

Wanted Result:

cat{
    name:"pussy"
    owner:["peter"]
}

Answer 1

We JUST updated that section of the Realm documentation to clarify this behaviour.

Unfortunately, because 'nil' is also a valid value for every optional property of a Realm object, it's not possible for Realm to intelligently tell the difference between when an empty value supplied should be ignored, or should be used to empty the property it's pointing at.

The easiest way would be to use the JSON you've received to build an NSDictionary that only contains the value you wish to update, and then pass that to Realm through the +[RLMObject createOrUpdateInRealm:withValue:] to explicitly only update the properties on that object that you've supplied.

If you want to update your object using a RLMObject copy of that object, you'll need to make sure the copy contains all of the properties you want to keep.