currently the JSONStore API provides a load() method that says in the documentation:
This function always stores whatever it gets back from the adapter. If the data exists, it is duplicated in the collection". This means that if you want to avoid duplicates by calling load() on an already populated collection, you need to empty or drop the collection before. But if you want to be able to keep the elements you already have in the collection in case there is no more connectivity and your application goes for offline mode, you also need to keep track of these existing elements.
Since the API doesn't provide a "overwrite" option that would replace the existing elements in case the call to the adapter succeeds, I'm wondering what kind of logic should be put in place in order to manage both offline availability of data and capability to refresh at any time? It is not that obvious to manage all the failure cases by nesting the JS code due to the promises...
Thanks for your advices!
One approach to achieve this:
Use enhance to create your own load method (i.e.
loadAndOverwrite). You should have access to the all the variables kept inside an JSONStore instance (collection name, adapter name, adapter load procedure name, etc. -- you will probably use those variables in the invokeProcedure step below).Call push to make sure there are no local changes.
Call invokeProcedure to get data, all the variables you need should be provided in the context of enhance.
Find if the document already exists and then remove it. Use
{push: false}so JSONStore won't track that change.Use add to add the new/updated document. Use
{push: false}so JSONStore won't track that change.Alternatively, if the document exists you can use replace to update it.
Alternatively, you can use removeCollection and call load again to refresh the data.
There's an example that shows how to use all those API calls here.
Regarding promises, read this from InfoCenter and this from HTML5Rocks. Google can provide more information.