Creating a Breeze Entity including navigationproperties using manager.createEntity throws exception

Question

Scenario:

I use breeze for querying in our SPA and raw http methods for POST PUT DELETE methods. A POST method on a resource returns the created resource including it's created childobjects.

I want to attach this created resource to the beeze entity manager.

I've tried adding the entity using

manager.createEntity('Driver', data, breeze.EntityState.Unchanged);

where the data object contains the driver resource and an array of related child entities.

But get an exception: "Collection navigation properties may NOT be set."

Do I have to create the local entity by hand and attach the child entities or does breeze support this scenario?

Answer 1

The reason for this exception is that the 'createEntity' method creates the entity and then assigns your 'data' to it, but for any collection navigation properties the collection already exists and Breeze won't allow you to replace it. This was a deliberate choice for existing entities where other parts of the application might hold a reference to the collection, but is overkill in this case where you are the 'first' to access the collection. For now, the workaround is to update any navigation collections instead of replacing them.

So the simplest way to do this is to call the createEntity method without any collection data properties, and then push data into your collections

var driver = manager.createEntity('Driver', dataWithoutCollections, EntityState.Unchanged)
// then update collection properties by pushing into them.
trafficFines.forEach(function(trafficFine) {  
   driver.trafficFines.push(trafficFine);      // or use push.apply
};

Note that adding to an entity's collection properties will not cause an EntityState change so this should be sufficient.

Based on this issue, I will add a feature request to suppress this exception in the case where you are calling the 'createEntity' method, since there is no danger that some other part of the application has already had access to the new entity.