Knockout - readonly model binding from selected item in dropdown

http://stackoverflow.com/questions/9769955/knockout-readonly-model-binding-from-selected-item-in-dropdown

HTML

<script src="https://github.com/downloads/SteveSanderson/knockout/knockout-2.0.0.debug.js"></script>
<script src="https://raw.github.com/SteveSanderson/knockout.mapping/master/knockout.mapping.js"></script>
<div class="items_container">
   <!-- ko foreach: items -->
    <span data-bind="text: prop"></span>
    <a href="javascript:void(0);" data-bind="click: $parent.edit_item">edit</a>
    <br/>
       <!-- /ko -->
</div>

JavaScript

var Editor = function(v1) {
    var self = this;
    self.load_editor = function(item) {
        item.prop("Test4");
        console.log(item);
        return false;
    }
}

var sectionView = function() {
    var self = this;
    self.items = ko.observableArray();
    self.load_items = function() {
        setTimeout(function() {
            var items = [{
                prop: ko.observable('Test')},
            {
                prop: ko.observable('Test2')},
            {
                prop: ko.observable('Test3')}];
            self.items(items);
        }, 500);
    };
    self.edit_item = function(item) {
        if (self.editor == null) {
            self.editor = new Editor(self);
            self.editor.load_editor(item);
        }
    }
    ko.applyBindings(self, $('.items_container')[0]);
}

var v1 = new sectionView();
v1.load_items();