backbone parse return results array - backbone.js

Question

The restful api im calling wraps the desired payload (of models) within 'Payload'
I can ONLY get it to work this way, by 1. adding each into this.add(model) and 2. returning the array
Note: 'this' is a Backbone Collection
parse: function(resp, xhr) {
var that = this;
var ourPayload = resp.Payload;
ourPayload.forEach( function(model) { that.add(model);} );
return ourPayload;
},
In all examples I'd expect to simply do
parse: function(resp, xhr) {
return resp.Payload;
}
The format of the rest api is "{"Success":"true", ...., "Payload":[{model},{model},{model}], .... }
Can one explain the need to the collection.add(model)

Answer 1

The problem is that during a Collection fetch each Model's parse will also be called if they are defined. And likely the model's parse function will be defined in just this case: the RESTful API format is using a wrapper around the payload.
Backbone docs
After fetching a model or a collection, all defined parse functions
will now be run. So fetching a collection and getting back new models
could cause both the collection to parse the list, and then each model
to be parsed in turn, if you have both functions defined.
Therefore you need to define a parse as below. Note that 'Payload' is the name of your wrapper, be it payload, data, results,,
// Within a collection, it will not.
parse: function (response, xhr) {
if (_.isObject(response.Payload)) {
return response.Payload;
} else {
return response;
}
}
Now that clue came from nikoshr in this SO answer
Further in some cases, when your entrepid backend guy has wrapped a Model in an array then you gotta do the following with the Payload index [0]
parse: function (response, xhr) {
if (_.isObject(response.Payload)) {
return response.Payload[0];
} else {
return response;
}
}

Answer 2

This should work (it should be put into the collection):
parse: function (response) {
return response.Payload;
}
See the documentation. The Twitter Search API the doc refers to is documented here. The response you get has basically the same structure: you get an object, with a field containing the array of models. The same technique works well when one calls an ASMX webservice, see the example here.