Add "pluck" to quiver.mirrors

[seaneagan]

See http://underscorejs.org/#pluck

This doesn't fit in the core libraries, see http://dartbug.com/15278, since it requires mirrors.

Example implementation:

Iterable pluck(Iterable iterable, Symbol property) =>
    iterable.map((item) => reflect(item).getField(property).reflectee);

Usage:

main() {
  pluck([{'a': 1}, 'xx', [1, 2, 3]], #length).forEach(print);
}

Output:

1
2
3

[justinfagnani]

I'm not sure I'd like to see this do into to Quiver. It basically save 6 characters, but throws out all static checking along the way. It makes sense in JavaScript because there's no short lambda syntax and no static checking anyway.

Without pluck you can extract a property with:

[{'a': 1}, 'xx', [1, 2, 3]].map((e) => e.length);

Which I also think is clearer.

[seaneagan]

The main use case is when there is a dynamic property name, I was just too
lazy to come up with an example :). But I agree it may be too specialized
for quiver. Thanks for the feedback!

Cheers,
Sean Eagan

On Mon, Nov 25, 2013 at 11:21 AM, Justin Fagnani
notifications@github.comwrote:

I'm not sure I'd like to see this do into to Quiver. It basically save 6
characters, but throws out all static checking along the way. It makes
sense in JavaScript because there's no short lambda syntax and no static
checking anyway.

Without pluck you can extract a property with:

[{'a': 1}, 'xx', [1, 2, 3]].map((e) => e.length);

Which I also think is clearer.

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