CODEWITHSUNDEEP
ruby-on-railsactiverecordhas-manybelongs-to
Techmago
Techmago

Reputation: 380

Rails no method error for empty relation

i just get an error.

i got a has many assotiations, but when filling a form, i leave the field empty, and ir returned me an error:

 Showing /home/techmago/namebook/app/views/names/index.html.erb where line #16 raised:

undefined method `nome' for nil:NilClass

Extracted source (around line #16):

13: <% @names.each do |name| %>
14:   <tr>
15:     <td><%= name.nome %></td>    
16:     <td><%= name.family.nome %></td>
17:     <td><%= name.race.nome %></td>
18:     <td><%= h(name.descr).gsub(/\n/, '<br/>').html_safe %></td>
19:     <td>

I am sure that is because one of the name.family.nome is nill. I would like that this situation could be accepted

Models:

class Name < ActiveRecord::Base
  belongs_to :family
  belongs_to :race
  has_and_belongs_to_many :books

  attr_accessible :descr, :family_id, :nome, :race_id, :book_ids

  validates :nome, presence: true
end

class Family < ActiveRecord::Base
  has_many :names
  has_and_belongs_to_many :books
  has_and_belongs_to_many :races

  attr_accessible :descr, :nome, :book_ids, :race_ids

  validates :nome, uniqueness: true, presence: true
end

Upvotes: 0

Views: 317

Answers (1)

pdobb
pdobb

Reputation: 18037

So what we know is that that name, in particular, doesn't have an associated family object. That is, name.family is returning nil, which doesn't respond to nome, as indicated by the error. So, if what you're looking for is that this be handled gracefully... i.e. don't error and don't show anything in this case, you can do this:

<%= name.family.try(:nome) %>

The try block will return nil if name.family is nil and then the erb block will return an empty string, basically.

Otherwise, you'll need to figure out why one of the names in the loop doesn't have a family and go from there.

Upvotes: 2

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