knockout js `create callback` used with mapping plugin when model's mapping written as a function

Question

I have a working jsfiddle here which is doing exactly what I want so far ie listing a bunch of contacts (using the mapping plugin) and extending each 'contact' with an additional observable isEnabled which is used to control the (enabled/disabled) status of the input boxes displayed in each row.

What I'm having trouble understanding, however, is how to code the contactsMapping as a function. Where I currently have:

var contactsMapping = {
    'contacts': {
        key: function (item) {
            return ko.utils.unwrapObservable(item.id);
        },
        create: function(options) {
           return new contactModel(options.data);
        }
    },
};

I want to use a function (for cleaner access to this etc as described variously):

var contactsMapping = function() {
    var self = this;

    // self.contacts = [what goes here??] 
};

contacts in this model is (educated guess) somehow transcribed by the mapping plugin as an observable array but, how do I inject the key and create functions correctly?

Thanks for any help/pointers...

Answer 1

The mapping functions accept a third parameter which is the object the mapped values are injected into (is extended to). So if you wanted to extend to self, pass it in.

var contactsMapping = function (data) {
    var mappingOptions = {
        'contacts': {
            key: function (item) {
                return ko.utils.unwrapObservable(item.id);
            },
            create: function(options) {
                return new contactModel(options.data);
            }
        },
    };
    ko.mapping.fromJS(data, mappingOptions, this);
};

fiddle