Hi Robert. Firstly, I really like the approach of avoiding nil checks – good
choice for an article.
While reading your example code I got a bit confused though. I wouldn’t expect
the `#line_items` method to ever return `nil`, as I’d expect it to always
return a collection (ActiveRecord is so prevalent in Rails that I just assume
it).
So if there was a basket, but there weren’t any line items in it, I’d expect to
get an empty array.
Later on, when you introduce `MissingBasket` I get the feeling that
substituting it for a `nil` basket might have been what you actually intended.
In case my description is hard to follow, I’m saying I think you probably meant
to write something like this:
<% if @basket.present? %>
<% @basket.line_items.each do |item| %>
<p><%= item %></p>
<% end %>
<% end %>
I think there’d be less potential for people to get tripped up by this if you
changed the example code so that `@basket` is `nil`, rather than having
`Basket#line_items` returning `nil`.
Also, whether you need a unit test for the `if` is a slightly contentious one
(I suspect the more testing you do the less important such tests seem), so (in
order to prevent the reader from getting distracted by it) I’d probably remove
that paragraph if I was you. I don’t think you need it to reinforce the
benefits of the Null object pattern anyway – it’s undeniably cleaner to just
avoid the conditional.
Cheers,
Graham
On Tue, 23 Feb 2016, at 11:47 AM, Robert Whittaker wrote:
> In an attempt to get them to share more, I have asked my team at On the Beach
> to submit a blog post every month about something they have learned. Today, I
> submitted my first article!
>
> http://purinkle.co.uk/post/139843782736/on-the-if
>
> Let me know your thoughts. Here are some helpful links just in case you want
> to share.
>
> * https://twitter.com/purinkle/status/702084436234477568
> * https://www.facebook.com/purinkle/posts/10100204829015603
> * https://plus.google.com/115653446145456682786/posts/MoKipM4pr1W
> * https://www.reddit.com/r/ruby/comments/476406/on_the_if/
> * https://www.reddit.com/r/programming/comments/47650b/on_the_if/
> * https://news.ycombinator.com/item?id=11158011
>
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