Re: [Rails] in standby for an annoying problem.

On 15 November 2012 09:11, Jim Ruther Nill <jvnill@gmail.com> wrote:
>
>
>
> On Thu, Nov 15, 2012 at 4:51 PM, Colin Law <clanlaw@googlemail.com> wrote:
>>
>> On 15 November 2012 08:09, Mauro <mrsanna1@gmail.com> wrote:
>> > On 14 November 2012 22:21, Colin Law <clanlaw@googlemail.com> wrote:
>> >> On 14 November 2012 21:07, Mauro <mrsanna1@gmail.com> wrote:
>> >>> I have a model Reservation with reserved_from and reserve_to
>> >>> attributes of type date.
>> >>> I want create a scope of all reservations where Date.today is between
>> >>> reserved_from and reserved_to.
>> >>> In the model I've done:
>> >>>
>> >>> def self.today_reservation
>> >>> find_each do |res|
>> >>> if (Date.today).between?(res.reserved_from, res.reserved_to)
>> >>> return
>> >>> else
>> >>> puts "false"
>> >>> end
>> >>> end
>> >>> end
>> >>> scope :today_reservations, today_reservation
>> >>>
>> >>> but it doesn't work.
>> >>> If reserved_from is 2012-11-01 and reserved_to is 2012-11-02 and
>> >>> Date.today is 2012-11-14 the method above method return an
>> >>> activerecord relation.
>> >>
>> >> That is not how scopes work. You need something like (not tested)
>> >> scope :today_reservations, lambda { where("reserved_from > ? and
>> >> reserved_to <= ?", Date.today, Date.today ) }
>> >
>> > Without lamda it's the same thing?
>> > scope :today_reservations, where("reserved_from > ? and
>> >> reserved_to <= ?", Date.today, Date.today ) works the same.
>>
>> No it doesn't. Well it does today but if you don't restart the server
>> then it won't work tomorrow. Without the lambda it is determining
>> Date.today only once when it loads that line of code. You need the
>> lambda so that it recalculates it every time you run the scope.
>
>
> Colin is right but you can also use class methods so you dont have to worry
> about
> adding lambdas
>
> def self.today_reservations
> where('reserved_from > :date AND reserved_to <= :date', date: Date.today)
> end

Does that have any advantage over using a scope? It has the
disadvantage that one could not say things like
Reservation.where(some conditions).today_reservations

In fact I think my previous comment only applies to production mode
since the code would be reloaded for each request in development mode
and so all would appear to work well - until deployment that is. I am
not even sure how to write a test that would fail for the code without
the lambda.

Colin

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