Question

I am trying to write a custom binding called divider.

Its simply splice the passing observableArray object into smaller arrays and wrap its elements with a template. It is working but i am getting an error :

Uncaught Error: Unable to parse bindings.
Message: ReferenceError: list is not defined;
Bindings value: foreach : list

What is the problem here ? I can’t see 🙂

HTML

<form data-bind="divider : { size : 4, list: controls , templateName : 'unit' }" class="form-horizontal"></form>

<script id="unit" type="text/x-jquery-tmpl">
    <div class="control-group">
      <div class="box" data-bind="template: { name : 'controlTemplate', foreach : $data }"></div> 
    </div>
</script>

<script id="controlTemplate" type="text/x-jquery-tmpl">
  <label data-bind="text:label" class="control-label" />
  <div class="controls">
    : <input data-bind="value:value" type="text" class="input-small"></input>
  </div>
</script>

<script id="dividerTemplate" type="text/x-jquery-tmpl">
    <div class="dividerContainer"  data-bind="foreach : list ">
      <div class="divider" data-bind="template : { name : $parent.name }"></div>               
    </div>
</script>

JAVASCRIPT

function l(log) {
 console.log(log); 
}

function Control(label,value) { 
  var self = this;  
  this.label = ko.observable(label);
  this.value = ko.observable(value);
}

function ViewModel() {

  var self = this;  

  this.controls = ko.observableArray();  

  for(var i=1;i<=10;i++) {
    this.controls.push(new Control('TEST'+i,'VALUE'+i));
  }  
}  

ko.bindingHandlers.divider = {

    init: function (element, valueAccessor, allBindingsAccessor, data, context) {

      var defaultOptions = { size : 5 };
      var options = $.extend(true, defaultOptions, valueAccessor()); 

      var seperatedList = ko.observable([]);

      if( options.list().length > 0 && options.templateName !== null) {

        var length = options.list().length;
        var size = options.size;
        var templateName = options.templateName;

        for(var i=0; i< (length/size); i++)          
                seperatedList().push(options.list.slice(i*size, (i+1)*size) );

        l(ko.toJSON(seperatedList));

        ko.applyBindingsToNode(  $(element).get(0),
                                 {template: { name: 'dividerTemplate' , data : { list: seperatedList , name : templateName}} }
                              );
        }

    }
};

$(document).ready(function(){

  var viewModel = new ViewModel();  
  ko.applyBindings(viewModel);

});

JSFIDDLE

Answer 1

You will want to have your custom binding’s init function return:

      return { controlsDescendantBindings: true };

This makes sure that the main binding loop does not try to apply bindings to the new elements that were rendered as a result of you manually calling the template binding from your binding.

Some extra information: here and here