How to use a knockout component view with parent layout?

Question

I am working on replacement ASP.NET MVC+Knockout with just Knockout, I want to remove ASP.NET and get just static js + html.

My ASP.NET views consist of Partial views (I call them widgets in my project), this Partial views easily replaced with Knockout components.. but I have a problem: ASP.NET Partial views have a Layout (some html decoration for every widget), how can I achieve similar for Knockout component view?

Simplified example. Old asp.net scheme:

View.cshtml:

<div>
    @Html.Partial("SomeWidget")
</div>

SomeWidget.cshtml:

@{
    Layout = "~/Views/Shared/_WidgetLayout.cshtml"; <!-- parent layout for widget -->
}
<span>This is some widget</span>

_WidgetLayout.cshtml:

<div>
    <span>This is decorator for every widget</span>
    @RenderBody() <!-- render widget view here (SomeWidget.cshtml in this example) -->
</div>

New knockout-only scheme:

View.html:

<div>
    <some-widget></some-widget>
</div>

View.js:

ko.components.register('some-widget', { require: 'app/SomeWidget' });

SomeWidget.html:

<span>This is some widget</span>

SomeWidget.js:

var view = require('text!/views/SomeWidget.html');
return { template: view };

How to replace _WidgetLayout.cshtml in Knockout?

Answer 1

There are several ways you could possibly do this. The simplest way I can think of is to have a template component, and you nest the widget inside this. KO Components support nesting.

You can define a template component thus:

    ko.components.register("widget-template", {
        viewModel: function(params) {
            var self=this;
            self.WidgetName = params.widget;
        },
        template: "<div class='b'><span>This is decorator for every widget</i>
<div data-bind='component: { name: WidgetName }'></div></div>"
    });

To use this, you put the template-widget into your HTML, and pass the name of the widget as a parameter:

<widget-template params="widget: 'widget1'"></widget-template>

Then you define a widget as another component:

ko.components.register("widget1", {
    template: "<h3>Widget One</h3>"});

So now you have a re-usable template that can wrap any component. You can see more about this binding in the Knockout documentation.

See the full JS fiddle here: http://jsfiddle.net/Quango/a8h2bwtc/

Note that you can also make the name an observable rather than a static value, as seen here: http://jsfiddle.net/Quango/tnphvvgd/