I see. You can match on both or use a with in this case:
if membership_ends_on || trial_ends_on || dues_exempt? do
changeset
else
add_error(changeset, :membership_ends_on, "is required")
end
On Wed, Dec 23, 2020 at 7:50 PM Moxley Stratton <moxley.strat...@gmail.com>
wrote:
> 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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>>>>>
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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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