[Feature request] Whitelisting which components can render within a block component

[olivierlesnicki]

It looks like the framework doesn't support a default way of whitelisting which components can render within its yield.

{{#parent-component 
  as |first-child second-child|
}}
  {{first-child}}
  {{second-child}}
  Hello World.
{{/parent-component}}

The requirement is to be able to render {{first-child}} and {{second-child}} because they're components supplied by the parent-component but not render "hello world." or any other component/data for that matter.

A workaround is today's possible with ember-wormhole where the parent-component can have the following template:

// parent-component
<div id="first-child">
</div>
<div id="second-child">
</div>
<div style="display:none;">
  {{yield}}
</div>

And the first-child:

// first-child
{{ember-wormhole to="first-child"}}
  ...
{{/ember-wormhole}}

While it does achieve the required requirement I think it's important for a framework that offers composability to be able to handle.

Because react requires you to define the template within the render hook you're able to do it quite easily:

render() {
  return (
   <div>
     {this.props.children.filter(child => {
        return child instaceof FirstChild || child instanceof SecondChild;
     })
   </div>
  );
}

Maybe there's a way to do it which I wasn't able to find on StackOverflow nor ember set of documentation.

[rwjblue]

I do not think there is a way to do this, but I'm not really sure why you would want to...

Either way I don't see this as a bug in the framework, which is what we use issues in this repo for. We track feature requests as issues in the github.com/emberjs/rfcs repo (and feature proposals as PR's to the same repo). Would you mind submitting over there?