Yeah that macro would be quite useful. This Const I would use on such
bounds, I just hate magic numbers in the code even at the bounds, hence
helper methods.
On Friday, September 2, 2016 at 8:41:05 AM UTC-6, Michał Muskała wrote:
>
> While I can see the appeal of such solutions I'd say the usual way to deal
> with such things is to use atoms and do the conversion on the system
> boundry. You convert to atom the incoming params as soon as you can, and
> you convert back to the integer value just before sending it out.
> In general you only need two functions: to_atom/1 and from_atom/1, you can
> even automate generating them with a macro:
>
> @mapping [foo: 1, bar: 2]
>
> for {key, value} <- @mapping do
> def to_atom(unquote(value)), do: unquote(atom)
> def from_atom(unquote(atom)), do: unquote(value)
> end
>
> This has the huge advantage of a meaningful value for debugging and
> maintaining the same speed (atoms are more-or-less integers at runtime).
>
> Michał.
>
> > On 31 Aug 2016, at 07:53, Michele Balistreri <a...@bitgamma.com
> <javascript:>> wrote:
> >
> > Macro would also be possible, but in that case you would have to require
> the module to use its constants. I agree however that being useable in
> guards is a good point. PRs are always welcome.
> >
> > Regarding allowing non-integer values, I do not know if it makes much
> sense. The entire point of defining constants this way is to be able to
> interface with external services/serialization. If you can use Elixir terms
> then you probably do not need this. Or am I missing something?
> >
> > On Tuesday, August 30, 2016 at 5:14:19 PM UTC+3, OvermindDL1 wrote:
> > I actually do use a lot of `defmacro something, do: 42` for enums
> operating with a remote system, this would be convenient. :-)
> >
> > Have you thought about making it a macro (be sure to escape the return
> in case they want the value to be a tuple or so), that way it can be used
> in more areas and in matching?
> >
> > On Monday, August 29, 2016 at 11:52:44 PM UTC-6, Michele Balistreri
> wrote:
> > Hi all,
> >
> > after reading the topic at
> http://stackoverflow.com/questions/33851536/how-do-you-define-constants-in-elixir-modules
>
> I decided to use the approach taken by wxErlang. I found this to be a
> little verbose, especially since I also needed a list of all constants and
> an easy way to convert from the integer value to the associated atom.
> >
> > So I created the const package, which allows you to write this:
> >
> > defmodule Status do
> > use Const, [:queued, :processed, :sent]
> > end
> >
> > and obtain this
> >
> > defmodule Status do
> > def queued, do: 0
> > def processed, do: 1
> > def sent, do: 2
> > def all, do: [queued: 0, processed: 1, sent: 2]
> > def by_value(val) do
> > # returns the atom from the integer value. In case of duplicated
> values, the fist
> > # associated atom is returned
> > end
> > end
> >
> > You can also give a keyword list if you need specific values, and even a
> list where some elements are just atoms and some are tuples. The behavior
> in this case will be like for C enums.
> >
> > More details at: https://github.com/bitgamma/const
> >
> > Hope it can be useful!
> >
> > Regards,
> > Michele Balistreri
> > Bitgamma OÜ
> >
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