Getting selected item(s) in "checkboxes"

[fabiomcj]

Hi, I would not make a trivial question, but how can I get the "selected items" of the checkboxes in a function of my controller?
This is my use case: I have some checkboxes, I want to call a function every time an item is selected. inside this function I must know what item(s) is selected because for each item I want to perform different actions (like adding some extra field in my form schema and definition).
This is my approach:
Schema:

{
            type : "object",
            title : "Reporting",
            properties : {
            ......
                needs_procedures : {
                    type : "array",
                    items : {
                        type : "string",
                        enum : [ "1", "2", "3" ]
                    }
                }

            }
}

FormDef:

{
    type : "section",
    htmlClass : "col-xs-6",
    items : [ {
        key : "needs_procedures",
        title : "Procedures",
        type : "checkboxes",
            onChange : "itemSelected(form.key, model.needs_procedures)",
        titleMap : [ {
                value : "1",
                name : "pneumological examination"
                }, {
                value : "2",
                name : "cardiologic examination"
                    }, {
                value : "3",
                name : "spirometry"
                }, {
                value : "4",
                name : "electrocardiogram"
                } ],
                } ]
            }

"needs_procedures" field is inside a section, that is inside a section, that is inside a fieldset, that is inside a tab structure.
In my controller

$scope.itemSelected = function(key, value) {
        console.log(key);
        console.log(value);     
    };

The First time that an element is checked the function itemSelected() is called, but in the second parameter I have a empty array.
The second time I have an array with one element: the previous...
the third time I have an array with two elements: the two previous...
and so on...
Then it is as if the method is invoked immediately before the model is updated.

[Anthropic]

@fabiomcj can you make a plunker demo or gist for us?

[Anthropic]

We are probably going to add arrayIndeces soon so you can traverse your model more easily. But a plunker/gist would help.

[Anthropic]

Please re-open if you can provide more information to help us to help you :)