javascript – Access $parent's $parent in knockout view – nesting context-ThrowExceptions

Exception or error:

Updated for brevity

How can I reference the $parents’ $parent in nested Knockout foreach / with bindings?

Example –

    <!-- ko foreach: grandParent -->
        <tr>
            <!-- ko foreach: $parent.parents --> // <-- Doesn't work
                <!-- ko foreach: children -->
                    <td data-bind="if: favToy().name == $parent.$parent.favToy().name">
                        <span data-bind="text: favToy().name"></span>
                    </td>
                <!-- /ko -->
            <!-- /ko -->
        </tr>
    <!-- /ko -->

Original

Sorry for the confusing question but I am trying to reach a second level parent’s value to check against a value in the current context (like below) to only show a span if it matches a $parent’s $parent’s value (ugh!)

    <!-- ko foreach: grandParent -->
        <tr>
            <!-- ko foreach: $parent.parents -->
                <!-- ko foreach: children -->
                    <td data-bind="if: favToy().name == $parent.$parent.favToy().name">
                        <span data-bind="text: favToy().name"></span>
                    </td>
                <!-- /ko -->
            <!-- /ko -->
        </tr>
    <!-- /ko -->

It would be easier to do it this way but from what I have read this is not possible or I am doing it wrong 🙂

    <!-- ko foreach: grandParent -->
        <tr>
            <!-- ko foreach: $parent.parents -->
                <!-- ko foreach: children ? favToy().name == $parent.$parent.favToy().name -->
                    <td  data-bind="text: favToy().name"></td>
                <!-- /ko -->
            <!-- /ko -->
        </tr>
    <!-- /ko -->

Any help would be greatly appreciated.

How to solve:

Use the $parents array, the grandparent would be $parents[1]. You may also be able to use $root if the grandParent object in your example is the topmost parent.

From the docs:

$parents

This is an array representing all of the parent view models:

$parents[0] is the view model from the parent context (i.e., it’s the
same as $parent)

$parents[1] is the view model from the grandparent context

$parents[2] is the view model from the great-grandparent context

… and so on.

$root

This is the main view model object in the root context, i.e., the
topmost parent context. It’s usually the object that was passed to
ko.applyBindings. It is equivalent to $parents[$parents.length – 1].

###

You can use $parentContext.$parent.

$parentContext provide many useful properties such as ($data, $parent, $index, …)

###

I think it would be easier to use the noChildContext setting like this:

Using “as” without creating a child context

The default behavior of the as option is to add a name for the current item while still also binding the contents to the item. But you may prefer keep the context unchanged and only set the name of the current item. This latter behavior will probably be the default in a future version of Knockout. To turn it on for a specific binding, set the noChildContext option to true. When this option is used along with as, all access to the array items must be through the given name, and $data will remain set to the outer viewmodel. For example:

<ul data-bind="foreach: { data: categories, as: 'category', noChildContext: true }">
    <li>
        <ul data-bind="foreach: { data: category.items, as: 'item', noChildContext: true }">
            <li>
                <span data-bind="text: category.name"></span>:
                <span data-bind="text: item"></span>
            </li>
        </ul>
    </li>
</ul>

Read more here

Leave a Reply

Your email address will not be published. Required fields are marked *