José:
I agree on your first example.
Your second example wouldn't work:
case membership_ends_on || trial_ends_on || dues_exempt do
nil -> add_error(changeset, :membership_ends_on, "is required")
_ -> changeset
end
It wouldn't work because `dues_exempt` is a boolean. If `dues_excempt` is
`false`, it wouldn't match the `nil` clause.
On Wed, Dec 23, 2020 at 10:39 AM José Valim <jose.va...@dashbit.co> wrote:
> Thank you for the examples.
>
> However, I believe those examples are not really checking for a boolean,
> but rather for nil. If you don't want to use is_nil, you can always compare
> with nil, which is also pipeable:
>
> def has_access? do
> at_least_logged_in? and get_csrf_cookie(session) != nil
> end
>
> %{event_form | submitted: event_form.submitted_at != nil}
>
> case membership_ends_on || trial_ends_on || dues_exempt do
> nil -> add_error(changeset, :membership_ends_on, "is required")
> _ -> changeset
> end
>
>
> On Wed, Dec 23, 2020 at 7:04 PM Bruce Tate <br...@grox.io> wrote:
>
>> I support this feature. The arguments for
>>
>>
>> - a solution that composes well with pipes and
>> - the linters rejecting the most common solution of !!
>>
>>
>> are all particularly good ones. From my perspective, I teach composition
>> with pipes in the core, `with` in the boundary, and I try to have students
>> return a boolean rather than a truthy result as part of good API design.
>>
>> The inability to convert from truthy to boolean has always felt like a
>> missing feature to me.
>>
>> -bt
>>
>> On Wed, Dec 23, 2020 at 10:42 AM Andrea Leopardi <an.leopa...@gmail.com>
>> wrote:
>>
>>> What's the particular advantage of "to_boolean(term)" over "not
>>> is_nil(term)"? That it supports also booleans, which however could be used
>>> directly in predicates?
>>>
>>> Andrea
>>>
>>> On Wed, Dec 23, 2020 at 4:32 PM Moxley Stratton <
>>> moxley.strat...@gmail.com> wrote:
>>>
>>>> Here are examples:
>>>>
>>>> def has_access? do
>>>> at_least_logged_in? and !!get_csrf_cookie(session)
>>>> end
>>>>
>>>> %{event_form | submitted: !!event_form.submitted_at}
>>>>
>>>> case !!(membership_ends_on || trial_ends_on || dues_exempt) do
>>>> true -> changeset
>>>> false -> add_error(changeset, :membership_ends_on, "is required")
>>>> end
>>>>
>>>> case !!previous_value and !!new_value do
>>>> true -> put_change(changeset, :unconfirmed_email, new_value)
>>>> false -> changeset
>>>> end
>>>>
>>>> submitted? = !!Ecto.Changeset.get_change(changeset, :submitted_at)
>>>>
>>>> %{rsvpd: !!participation.rsvpd}
>>>>
>>>> On Tue, Dec 22, 2020 at 11:48 PM José Valim <jose.va...@dashbit.co>
>>>> wrote:
>>>>
>>>>> Can we revisit in which scenarios an explicit boolean conversion is
>>>>> necessary?
>>>>>
>>>>> On Wed, Dec 23, 2020 at 1:21 AM Moxley Stratton <
>>>>> moxley.strat...@gmail.com> wrote:
>>>>>
>>>>>> I would like revisit this issue.
>>>>>>
>>>>>> The issue was last discussed 5 years ago. Much has changed in that
>>>>>> time. The given solution was to use a double-negative (!!) to convert a
>>>>>> given value to a pure boolean.
>>>>>>
>>>>>> Here are the problems with the suggested solution:
>>>>>> 1. I believe this solution is a hack that is not intuitive to
>>>>>> beginners. It's rarely seen by mid and senior developers, meaning they
>>>>>> have
>>>>>> to pause to interpret what !! means.
>>>>>> 2. A double negative can't be part of an Elixir pipeline.
>>>>>> 3. The Credo package warns about double negatives: "Double boolean
>>>>>> negation found". Linters in other languages have a similar warning. Other
>>>>>> languages have a built-in function (JavaScript has Boolean()) to convert
>>>>>> to
>>>>>> boolean.
>>>>>> 4. The alternative to double-negative is verbose: "if expr, do: true,
>>>>>> else: false", or the less readable "expr && true || false"
>>>>>>
>>>>>> I would be happy to submit a PR to add Kernel.to_boolean/1.
>>>>>>
>>>>>> On Sunday, November 1, 2015 at 5:48:28 AM UTC-8 José Valim wrote:
>>>>>>
>>>>>>> Not necessarily , but the ones in Kernel are. :)
>>>>>>>
>>>>>>> --
>>>>>>>
>>>>>>>
>>>>>>> *José Valim*
>>>>>>> www.plataformatec.com.br
>>>>>>> Skype: jv.ptec
>>>>>>> Founder and Director of R&D
>>>>>>>
>>>>>> --
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>>>>>> .
>>>>>>
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>>>
>>
>>
>> --
>>
>> Regards,
>> Bruce Tate
>> CEO
>>
>>
>> <https://bowtie.mailbutler.io/tracking/hit/f8218219-d2a8-4de4-9fef-1cdde6e723f6/c7c97460-016e-45fb-a4ab-0a70318c7b97>
>>
>> Groxio, LLC.
>> 512.799.9366
>> br...@grox.io
>> grox.io
>>
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