CODEWITHSUNDEEP
iosjsoncore-datarestkit
Rengers
Rengers

Reputation: 15238

RestKit POSTed managed object becomes duplicate when response is enveloped in an array

When I POST a Core Data managed object using RestKit, RestKit doesn't update the existing object but creates a new object instead.

The returned JSON always contains the newly created object, but wraps it into a plural keyed array. I found that if I change this to just the one object, the updating works as expected. However, I would like to keep the array in the response so that all responses are consistently in the plural form.

Is there any way I can make RestKit update the record, even when returned from the server wrapped in an array?

Possible solution: identificationAttribute?

On my entities I have an identificationAttribute called remoteID. This is the primary unique key of the record. This will be 0 before the POST, because the object is not yet on the server. I thought that by adding a second identificationAttribute called insertionID, setting that before the POST, and then returning it in the response, would allow RK to find the existing entity in the local store. Alas, it didn't work.

What did work however, was setting the remoteID before the POST, to the next auto increment value on the server! What could explain that it works with remoteID, but not with a second insertionID?

Example request

{
    "user": {
        "email": "[email protected]"
    }
}

Response

{
    "users": [{
        "email": "[email protected]"
    }]
}

Upvotes: 1

Views: 167

Answers (1)

Wain
Wain

Reputation: 119031

I would like to keep the array in the response so that all responses are consistently in the plural form.

You shouldn't, because this is an individual request and response, not a composite.

Your idea about identificationAttribute is correct, but doesn't apply when the response is an array. The array is the trigger (or one of the possible triggers) to abandon the match with the source object and create new objects. Changing this would be hard.

Without knowing more about your real situation, 2 alternatives:

  1. Change the JSON
  2. POST a dictionary instead of the real object and then you won't have a duplicate

When you use multiple identification attributes, all must match for the destination object to be found.

Take care - don't create multiple mappings for the same entity with different identification attributes or you will most likely be debugging the lookup cache for a long time trying to work out what's happening...

If the identity matches before the request is made then the array isn't an issue. To explain the above in more detail:

When you POST an object, RestKit expects to get that object back. So, if you POST one object and get an array back it doesn't know what to do, because it can't map an array into an object. So, it tries to lookup based on the identification attribute (if they exist). If the POSTed object didn't have an id and the returned object does then it will never match. If you set it before POSTing then it will match.

Upvotes: 1

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