Creating a new kendo binding for "associative arrays" - kendo-ui

Question

I'll start off by stating that I don't know if this is possible at all, but I'm reading over the Kendo UI documentation and trying to figure out how to at least try it, but I'm running into a lot of difficulties with making a custom binding. This is a followup to another question I am still working on, which is posted here. If this is not an appropriate question, please kindly let me know, and I will close it or rephrase it. I'm just really lost and confused at this point.
As I understand it, based on what I've been told and tried, Kendo cannot bind to an Associative Array not because the data isn't good, but because it is an array of objects, each as a separate individual entity - under normal circumstances, an array would be a bit different and contain a length property, as well as some other functions in the array prototype that make iteration through it possible.
So I was trying to conjecture how to get around this. I succeeded in getting what I think was a workaround to function. I preface that with "think" because I'm still too inexperienced with Javascript to truly know the ramifications of doing it this way (performance, stability, etc)
Here is what I did;
kendo template
<script type="text/x-kendo-template" id="display-items-many">
# for(var key in data) { #
# if (data.hasOwnProperty(key) && data[key].hasOwnProperty("Id")) { #
<tr>
<td>
<strong>#= data[key].Id #</strong>
</td>
<td class="text-right">
<code>#= data[key].Total #</code>
</td>
</tr>
# } #
# } #
</script>
html
<table class="table borderless table-hover table-condensed" data-bind="source: Associative data-template="display-items-many">
</table>
Now to me, immediately off hand, this gave me the illusion of functioning. So I got to thinking a bit more on how to fix this ...
I want to create a new binding called repeat. The goal of this binding is as follows;
repeat the template for each instance of an object within the given root object that meets a given criteria
In my head, this would function like this;
<div data-template="repeater-sample" data-bind="repeat: Associative"></div>
<script type="text/x-kendo-template" id="repeater-sample">
<div> ${ data.Id }</div>
</script>
And the criteria would be a property simply called _associationKey. So the following would, in theory, work.
$.ajax({
// get data from server and such.
}).done(function(results){
// simple reference to the 'associative array' for easier to read code
var associative = results.AssociativeArray;
// this is a trait that everything in the 'associative array' should have to match
// this is purely, purely an example. Obviously you would use a more robust property
var match = "Id";
// go through the results and wire up the associative array objects
for(var key in associative ) {
if(associative.hasOwnProperty(key) && associative[key].hasOwnProperty(match)) {
associative[key]._associationKey = 10; // obviously an example value
}
}
// a watered down example implementation, obviously a real use would be more verbose
viewModel = kendo.observable({
// property = results.property
// property = results.property
associativeArray = associative
});
kendo.bind('body', viewModel);
});
So far this actually seems to work pretty well, but I have to hard code the logic in the template using inline scripting. That's kind of what I want to avoid.
Problem
The big issue is that I'm vastly confused on telerik's documentation for custom bindings (available here). I do have their examples to draw from, yes - but it's a bit confusing to me how it interacts with the object. I'll try to explain, but I'm so lost that it may be difficult.
This is what telerik gives for an example custom binding, and I've pruned it a bit for space concerns;
<script>
kendo.data.binders.repeater = kendo.data.Binder.extend({
init: function(element, bindings, options) {
//call the base constructor
kendo.data.Binder.fn.init.call(this, element, bindings, options);
var that = this;
// how do we interact with the data that was bound?
}
});
</script>
So essentially that's where I am lost. I'm having a big disconnect figuring out how to interact with the actual "associative array" that is bound using data-bind="repeat: associativeArray"
So ..
I need to interact with the bound data (the entire 'associative array')
I need to be able to tell it to render the target template for each instance that matches
Further Updates
I have been digging through the kendo source code, and this is what I have so far - by taking the source binding as an example... but I'm still not getting the right results. Unfortunately this poses a few problems;
some of the functions are internal to kendo, I'm not sure how to get access to them without re-writing them. While I have the source and can do that, I'd prefer to make version agnostic code so that it can "plug in" to newer releases
I'm totally lost about what a lot of this does. I basically made a copy of the source binding and replaced it with my own syntax where possible, since the concept is fundamentally the same. I cannot figure out where to do the test for qualification to be rendered, if that makes sense.
I'm having a big logic disconnect here - there should ideally be some place where I can basically say ... If the current item that kendo is attempting to render in a template matches a criteria, render it. If not, pass it over and then another place where I tell it to iterate over every object in the 'associative array' so as to get to the point where I test it.
I feel just forcing a for loop in here will actually make this fire too many times, and I am getting pretty lost. Any help is greatly appreciated.
kendo.data.binders.repeat = kendo.data.Binder.extend({
init: function(element, bindings, options) {
kendo.data.Binder.fn.init.call(this, element, bindings, options);
var source = this.bindings.repeat.get();
if (source instanceof kendo.data.DataSource && options.autoBind !== false) {
source.fetch();
}
},
refresh: function(e) {
var that = this,
source = that.bindings.repeat.get();
if (source instanceof kendo.data.ObservableArray|| source instanceof kendo.data.DataSource) {
e = e || {};
if (e.action == "add") {
that.add(e.index, e.items);
} else if (e.action == "remove") {
that.remove(e.index, e.items);
} else if (e.action != "itemchange") {
that.render();
}
} else {
that.render();
}
},
container: function() {
var element = this.element;
if (element.nodeName.toLowerCase() == "table") {
if (!element.tBodies[0]) {
element.appendChild(document.createElement("tbody"));
}
element = element.tBodies[0];
}
return element;
},
template: function() {
var options = this.options,
template = options.template,
nodeName = this.container().nodeName.toLowerCase();
if (!template) {
if (nodeName == "select") {
if (options.valueField || options.textField) {
template = kendo.format('<option value="#:{0}#">#:{1}#</option>',
options.valueField || options.textField, options.textField || options.valueField);
} else {
template = "<option>#:data#</option>";
}
} else if (nodeName == "tbody") {
template = "<tr><td>#:data#</td></tr>";
} else if (nodeName == "ul" || nodeName == "ol") {
template = "<li>#:data#</li>";
} else {
template = "#:data#";
}
template = kendo.template(template);
}
return template;
},
add: function(index, items) {
var element = this.container(),
parents,
idx,
length,
child,
clone = element.cloneNode(false),
reference = element.children[index];
$(clone).html(kendo.render(this.template(), items));
if (clone.children.length) {
parents = this.bindings.repeat._parents();
for (idx = 0, length = items.length; idx < length; idx++) {
child = clone.children[0];
element.insertBefore(child, reference || null);
bindElement(child, items[idx], this.options.roles, [items[idx]].concat(parents));
}
}
},
remove: function(index, items) {
var idx, element = this.container();
for (idx = 0; idx < items.length; idx++) {
var child = element.children[index];
unbindElementTree(child);
element.removeChild(child);
}
},
render: function() {
var source = this.bindings.repeat.get(),
parents,
idx,
length,
element = this.container(),
template = this.template();
if (source instanceof kendo.data.DataSource) {
source = source.view();
}
if (!(source instanceof kendo.data.ObservableArray) && toString.call(source) !== "[object Array]") {
source = [source];
}
if (this.bindings.template) {
unbindElementChildren(element);
$(element).html(this.bindings.template.render(source));
if (element.children.length) {
parents = this.bindings.repeat._parents();
for (idx = 0, length = source.length; idx < length; idx++) {
bindElement(element.children[idx], source[idx], this.options.roles, [source[idx]].concat(parents));
}
}
}
else {
$(element).html(kendo.render(template, source));
}
}
});

Answer 1

I would propose as a simpler solution transform transmitted associative array in an array. This is pretty simple and (for most cases) can solve your problem.
Lets say that you get the following associative array received from the server:
{
"One" : { Name: "One", Id: "id/one" },
"Two" : { Name: "Two", Id: "id/two" },
"Three" : { Name: "Three", Id: "id/three" }
}
That is store in a variable called input. Transform it from associative to no associative is as easy as:
var output = [];
$.each(input, function(idx, elem) {
elem.index = idx;
output.push(elem);
});
Now, you have in output an equivalent array where I saved the index field into a field called index for each element of the associative array.
Now you can use out-of-the-box code for displaying the data received from the server.
See it in action here : http://jsfiddle.net/OnaBai/AGfWc/
You can even use KendoUI DataSource for retrieving and transforming the data by using DataSource.schema.parse method as:
var dataSource = new kendo.data.DataSource({
transport: {
read: ...
},
schema : {
parse: function (response) {
var output = [];
$.each(response, function(idx, elem) {
elem.index = idx;
output.push(elem);
});
return output;
}
}
});
and your model would be:
var viewModel = new kendo.data.ObservableObject({
Id: "test/id",
Associative: dataSource
});
You can see it in action here: http://jsfiddle.net/OnaBai/AGfWc/1/