Hi Abdel,
sorry for the confusion, I guess I didn't explain myself properly. `orders`
would be a collection composed by instances of Order model. For example,
imagine you do `Order.last(5)` to get the last 5 orders. I hope this
clarifies the example.
Cheers,
Alberto
2018-05-16 18:50 GMT+02:00 Abdel Latif <mlotfi2...@gmail.com>:
> Hi,
> I am new to Ruby, can you please give me an example of the orders
> collection ?
> Thanks.
>
> On Wed, May 16, 2018 at 9:45 AM, Matt Jones <al2o...@gmail.com> wrote:
>
>>
>> On May 11, 2018, at 1:10 PM, Alberto Almagro <albertoalma...@gmail.com>
>> wrote:
>>
>> These days I have been comparing records in my daily job lots of times,
>> which made me think about a better way to retrieve and compare them. When I
>> want to navigate through several relations in a collection I often see
>> myself writing code like the following:
>>
>> Given orders as a collection of Order:
>>
>> > orders.map(&:order_option).map(&:item).map(&:title)
>>
>> => ['Foo', 'Bar', 'Baz']
>>
>>
>> That is, chaining maps with Symbol to Proc coercions one after each
>> other. Sharing my thoughts with my company's architect we came up with the
>> alternative:
>>
>> > orders.map { |order| order&.order_option&.item&.title }
>>
>> Very small nitpick: the code above (which tolerates `nil`) isn’t
>> equivalent to the chained map (which doesn’t). But anyways...
>>
>>
>> But we agreed that the notation was awful and didn't improve what we had
>> before. With this, I proposed what I think it is more like what we would
>> expect Ruby to have. I would like to add a notation similar to the one
>> we can find at Array#dig
>> <https://ruby-doc.org/core-2.5.0/Array.html#method-i-dig> or Hash#dig
>> <https://ruby-doc.org/core-2.5.0/Hash.html#method-i-dig> in the
>> following manner:
>>
>> > orders.map(&:order_option, &:item, &:title)
>>
>> The method doesn't necessarily need to be named map or collect, we can
>> agree on a different name for it if you want. Please share your thoughts
>> with me. If you like this, I would be very happy to write a PR to include
>> it in Rails.
>>
>>
>> This reminds me of the Elixir function `get_in` and the associated
>> functions in `Elixir.Access`. I’m not sure if any of the existing methods
>> would make sense to extend with the behavior, though:
>>
>> * `dig` is called on a collection and returns one element with many
>> levels of nesting
>> * `pluck` is called on a collection and returns a collection, but only at
>> one level of nesting
>> * the proposed function is called on a collection and returns a
>> collection, with many levels of nesting
>>
>> Neither function can guarantee that its arguments are scalars (or even
>> that they aren’t Procs, for that matter) so extending them is tricky.
>> Probably better to pick a new name.
>>
>> You might also consider “Proc#*” from Facets:
>>
>> https://github.com/rubyworks/facets/blob/master/lib/core/fac
>> ets/proc/compose.rb
>>
>> I haven’t tried it, but in principle this should work if the operator
>> precedence goes correctly:
>>
>> orders.map(&:order_options * &:item * &:title)
>>
>> —Matt Jones
>>
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