Question

I am looking for a library or framework that does JSON to Objective-C relational object mapping.
i.e. I need to map JSON containing objects, array of objects and dictionaries of objects to my custom objects.

something like:

DataObject {
    "user" : {
        "name":"Peter",
        "id":1234
    }
    "place": "UK"
    "job": {
        "title" : "CTO",
        "salary" : 1234567
    }
    "employess": [
        {
            "name":"Carlton",
            "id":1235
        },
        {
            "name":"Hugo",
            "id":12346
        }]
}

So there is a DataObject a UserObject and an employees array consisting of UserObjects.
I would like for the mapping from the JSON to my DataObject to happen “automatically”, of course meant as I would like to describe the objects and there relations in the Object class and have the mapping done from this, instead of manually mapping each nested object.
(First level native objective-c properties are easily done with setValue:forKey and other KVO methods, but from there on it gets complicated).

I have been testing out RestKit but it seems there is no way to pick and choose which functionality you need from that framework, it is either all of it or none of it, and I do find it does too much for my needs.

Are anyone familiar with a library etc. out there that can do this?

Thank you in advance.

Answer 1

What you have posted above isn’t valid JSON. If you made it valid JSON what you want to do is impossible without a specific schema, eg.

{
    "DataObject": {
        "user": {
            "name": "Peter",
            "id": 1234
        },
        "place": "UK",
        "job": {
            "title": "CTO",
            "salary": 1234567
        }
    }
}

Is Dataobject a dictionary or an Object? What about User or Job? What is User is an instance of NSUser and job is an NSDictionary?

On the other hand, if you have a known schema:-

[
    {
        "class": "DataObject",
        "properties": {
            "user": {
                "class": "User",
                "properties": {
                    "name": "Peter",
                    "id": 1234
                }
            },
            "place": "UK",
            "job": {
                "title": "CTO",
                "salary": 1234567
            }
        }
    }
]

you don’t need a framework as it is trivial to map to your objects yourself once you have valid JSON. Pseudocode:-

createWithDict(dict) {
    var newOb = create new(dict["class"]);
    dict.properties.each( val, key ) {
        if(val is dictionary && val.hasproperty("class"))
            val = createWithDict(val)
        newOb[key] = val
    }   
    return newOb;
}