Implement Query filters

[rkirov]

To support more flexible queries implement an option to pass filter to Query. For example: @Query(MyFeature.filter) list: QueryList<dynamic> where static filter(obj) => obj is Foo || obj is Bar.

see discussion on #1935 for more info.

[matanlurey]

👍

[rkirov]

Needs more design, as discussed passing every object through an opaque filter will prohibit further optimizations down the road.

[rkirov]

Discussed with Misko, we should tackle benchmarking query and performance improvements first before adding more general APIs.

[jhades]

I just wanted to mention that this feature could be more important than it might look at first sight. There are a lot of common use cases that seem to need this feature, take for example a menu with sub-menus:

<top-menu>
    <option title="Menu Entry 1"></option>
    <option title="Menu Entry 2 "></option>
    <option-group title="Menu Entry 3 dropdown Sub menu">
        <option title="sub-menu entry 1"></option>
        <option title="sub-menu entry 2"></option>
        <option-group title="Submenu entry 3 dropdown menu">
            <option title="Sub-Submenu entry 1"></option>
            <option title="Sub-Submenu entry 2"></option>
        </option-group>
    </option-group>
</top-menu>

In this case I believe we need to have in the top-menu @Component a QueryList of both the optionand option-group light-dom element directives. So we can loop over that list and render it as either an entry or a submenu.

Or is there some other alternative way of implementing this with the current API? Thanks

[mhevery]

Let's not implement this just yet, as it may have negative perf improvement. Let's make sure that we have real use cases, which can not be implemented in other ways.

[bduffany]

fyi this issue was referenced on StackOverflow: http://stackoverflow.com/questions/32300168/how-to-get-a-reference-to-a-particular-component-in-an-angular2-template

[mhevery]

I think the latest thinking is now, as it would prevent compile time generation of the queries. Will close.

/cc @tbosch

[bduffany]

@mhevery could you explain what you mean by that last comment?

[tbosch]

We will soon calculate the queries already during compilation.
With that, any filter function would need to be executed during compile
time as well. However, we don't have a good way to configure things that
need to run during compilation, as compilation will soon also run on the
server.

We could add a filter function that we just call on the query result, but
then there would be no benefit to a user filtering the result of a query
manually.
I would vote for not adding filters as it is one more concept that a user
has to learn, and does not provide a big benefit.

On Fri, Jan 29, 2016 at 10:20 AM Brandon Duffany notifications@github.com
wrote:

@mhevery https://github.com/mhevery could you explain what you mean by
that last comment?

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Reply to this email directly or view it on GitHub
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