Adapter Should Allow For Meta-Results

[ghempton]

Currently, RestAdapter expects everything in the returned JSON to correspond to model data. This is even more strictly enforced with the introduction of side-loading.

An extremely common scenario, however, is for the server to return metadata associated with the query, e.g. aggregate counts, pagination info, etc. The ability to capture this information is also the first step for features such as pagination.

[wycats]

How would you feel about loading metadata in a meta property?

[ghempton]

I am fine with that.

As far as storing the meta information is concerned, I currently attach it to the model array itself. Because I am trying to keep all this inside the adapter, this restricts metadata to the findQuery method as I am not given access to the model array inside findAll.

Another thought I have is that there might be some utility in allowing custom model array implementations: e.g. PaginatedModelArray etc.

[wagenet]

@ghempton Seems like you could do this in your adapter. If you need some hooks could you submit a PR?

[rlivsey]

What's the current thinking on this?

I'm currently doing as @ghempton mentioned and overriding didFindQuery in my adapter and attaching the meta to the recordArray but this feels wrong somehow.

There appears to be some support for the meta property now in the serializers since 1787bff, that commit mentions pagination as a use-case but I can't see how that would be implemented. extractMeta on the serializer doesn't have access to the records and so can't do anything useful with that data as far as I can make out.

[wildchild]

+1. Metadata makes sense. Guys, have you got a temp workaround?

[christophermanning]

When I attach meta like https://github.com/rails-api/active_model_serializers#attributes suggests, I don't see a way to access that data without a custom serializer since https://github.com/emberjs/data/blob/master/packages/ember-data/lib/serializers/json_serializer.js#L193-L198 doesn't make it accessible. Having the meta data available in a meta property would be great.

[mbrennan-afa]

👍 - Can we please have this re-evaluated.

[brennanmceachran]

Currently facing @christophermanning issue as well...

edit: Gotten around it by overwriting didFindQuery in my adapter:

    didFindQuery: function(store, type, payload, recordArray) {
        var loader = DS.loaderFor(store);

        loader.populateArray = function(data) {
            recordArray.load(data);

            // This adds the meta property returned from the server
            // onto the recordArray sent back
            recordArray.set('meta', payload.meta);
        };

        this.get('serializer').extractMany(loader, payload, type);
    }

[ghost]

I have submitted a PR (#815) which extends the functionality of the "meta" solution in 1787bff. It allows the use of custom meta properties, by passing them to the store typeMap.

[josepjaume]

I think the use case where you want to store metainformation of a query is pretty common and worth looking into it.

The solution @christophermanning is proposing sounds clean enough; why not have it implemented on the Adapter by default?

[sly7-7]

Since the #815 has been merged, does it solve it as well ?

[ghost]

The issue I had with the recordArray solution above is that if you execute a store.filter which calls findQuery, the recordArray returned does not contain the meta property. This is because what is returned is in fact a filteredRecordArray rather than the adapterPopulatedRecordArray returned by findQuery (where the meta property is set). Added to that (as mentioned above) this restricts any call that requires metadata to findQuery.

If you take a look at #815, it should solve these issues (it was specifically designed for this, as I had a need to send pagination data back from the server). There is a quick explanation of how it works with the ticket, but I am happy to create more in-depth examples if someone can suggest where I should place them, as we are yet to have ember-data docs.