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My first time asking. I'm in an internship so I'm not that proficient in Rails. Currently I'm working in a code that isn't mine, it has no automated tests and no documentation whatsoever, so I spent lots of time trying to understand what the functions does before actually writing some code.

My question:

What I'm trying to accomplish is to hide/omit a button, under a set of conditions.

My research:

Already searched everywhere but with no luck to my specific problem. Tried the solutions here: How to disable all form_for input fields in Ruby on Rails app? and here: In Rails edit action form, hide a form field. Also read rails documentation about form helpers: https://guides.rubyonrails.org/v4.2.10/form_helpers.html

The problem:

There is an object called school that is divided into Schools and SchoolGroup, theoretically schools that have children should be SchoolGroup. I'm trying to omit the Delete button to every SchoolGroup that have Schools associated with it.

If I put like this nothing happens

<% if school.children.length < 1 %>
<%= button_to 'Delete', school, :data => {:confirm => 'Are you sure you want to delete this school?'}, :method => :delete, :class=>"btn btn-sm btn-delete" %>
<% end %>

However if I put like this

<% if school.children.length > 0 %>

every button disappears!

So, I'm inferring that every school probably have children, even though it shouldn't and I need to ask for a different condition. Or should I try a controller-wise solution? If so, what can I do?

I'm using ruby 2.2.10 and rails 4.2.10.

Thank you all for your time and any help :)

Adriano
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  • is `current_school` distinct from some other collection of `school`s? – Aaron Breckenridge Aug 07 '18 at 16:31
  • No, it's actually the same thing, I will edit the question. Thank you for pointing that out. The results are the same. – Adriano Aug 07 '18 at 16:50
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    Do you have something like `school.children.new` somewhere? As a side note, you can use `if school.children.empty?`. – grilix Aug 07 '18 at 17:04
  • Yes! Thank you! `if school.children.empty?` worked like a charm. Such a simple solution. There is no `school.children.new` though, should be? – Adriano Aug 07 '18 at 17:11

1 Answers1

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The school.children.length returns the size of the collection. So,new child is also counted.

length() Returns the size of the collection calling size on the target. If the collection has been already loaded, length and size are equivalent. If not and you are going to need the records anyway this method will take one less query. Otherwise size is more efficient.

You can use school.children.count to count the records that persisted in the database. This method call will fire a database query.

neume
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