Hash#slice!

Rails
1

Hi,

One of the fundamental methods share by both ActiveSupport and Facets is
Hash#slice!. A few days ago, someone pointed out to me that the two libs
in this case are not quite the same. Quote, “I got hosed by a lovely bug
stemming from facets’ and rails’ slice! returning opposite things…
facets returns the key,value pairs not matched by the keys passed, great
because it gives you two things back at once, though slice and slice!
return different things. rails returns the key,value pairs matched,
that is, slice and slice! have the same return”

Generally I let Facets defer to the behavior of ActiveSupport when there
is a conflict, but in this case the Facets implementation seems more
useful and is also more in line to similar methods in core Ruby, ie.
Array#slice!, which also returns the deleted items.

So I was hoping that Rails could be modified to support this alternate
implementation of Hash#slice!.

Thanks,
T.

2

On 1 Sep 2008, at 00:28, Thomas S. <rails-mailing-list@andreas-
s.net> wrote:

facets returns the key,value pairs not matched by the keys passed,

So I was hoping that Rails could be modified to support this alternate
implementation of Hash#slice!.

Best place to discuss this is the rubyonrails-core mailing list.
Regardless of which way is “better” any change will have backwards
compatibility implications.

Fred

3

Frederick C. wrote:

Best place to discuss this is the rubyonrails-core mailing list.
Regardless of which way is “better” any change will have backwards
compatibility implications.

Thanks Fred. Your right it will have compatibility issues. However if
Matz is ever inclined to add Hash#slice! to Ruby itself, I am pretty
certain it will return the diff. Moreover, it is likely that very few
have used the return value slice! b/c it would be rather redundant (ie.
why would use #slice! when #slice works?)

I tried signing up to core list, but it is moderated and haven’t been
contacted yet. Hopefully soon.

T.

4

On Mon, Sep 1, 2008 at 2:14 PM, 7rans [email protected] wrote:

facets returns the key,value pairs not matched by the keys passed,

So I was hoping that Rails could be modified to support this alternate
implementation of Hash#slice!.

We do have tests which assert that that’s the result returned, but
they’ve been there from the beginning:

If you want to take a look at making that change, we can have a look
to see if it breaks anything else.

–
Cheers

Koz

5

On Sep 2, 11:48 am, “Michael K.” [email protected] wrote:

We do have tests which assert that that’s the result returned, but
they’ve been there from the beginning:

GitHub - rails/rails at 86deb270953f9c5b62813d3e1938f33cc807bd7f…

If you want to take a look at making that change, we can have a look
to see if it breaks anything else.

Ok. I’ve done it.

    # Replaces the hash with only the given keys.
    def slice!(*keys)
      keys = keys.map! { |key| convert_key(key) } if respond_to?

(:convert_key)
omit = slice(*self.keys - keys)
hash = slice(*keys)
replace(hash)
omit
end

I also updated the tests. Should I submit a patch? How do I proceed?

Thanks,
T.

6

I also updated the tests. Should I submit a patch? How do I proceed?

You should create a patch following the guidelines we have on
lighthouse:

http://rails.lighthouseapp.com/projects/8994/sending-patches

Once that’s done you can attach it to a new ticket and ask people for
feedback on it.

–
Cheers

Koz

7

On Sep 4, 4:13 am, “Michael K.” [email protected] wrote:

I also updated the tests. Should I submit a patch? How do I proceed?

You should create a patch following the guidelines we have on lighthouse:

http://rails.lighthouseapp.com/projects/8994/sending-patches

Once that’s done you can attach it to a new ticket and ask people for
feedback on it.

Done. Ticket #971.

Thanks for the help.

T.