I have a Rails app with two models that are associated:
class Person < ApplicationRecord
has_many :pets
has_many :toys
end
class Pet < ApplicationRecord
belongs_to :person
end
I want to fetch an instance variable in Pet from an instance of Person, however I am using metaprogramming to do this. I am using the following code:
<% if form.object.send(association).present? %>
<%= image_tag form.object.send(association).send(preview_url_attribute), class: options[:image_classes] %>
<% end %>
In the above example, form.object
is an instance of Person. association
is the name of the association between A and B (e.g. :pets
), and preview_url_attribute
is the name of the attribute in Pet that I want to fetch (e.g. :breed
).
Is there a better way to do this without using send
?
Yes, there is a more concise and readable way to fetch the desired attribute in the associated model without using send
. Instead, you can leverage the association methods provided by ActiveRecord associations.
Assuming you have the following code:
class Person < ApplicationRecord
has_many :pets
# ...
end
class Pet < ApplicationRecord
belongs_to :person
# ...
end
And you want to fetch the preview_url_attribute
from the associated pets
in the Person
model.
You can simplify the code in the view as follows:
<% if form.object.association(association).loaded? && form.object.association(association).any? %>
<%= image_tag form.object.association(association).first.public_send(preview_url_attribute), class: options[:image_classes] %>
<% end %>
Here's what changed:
-
Instead of using
send(association)
to fetch the associated records, you can useassociation(association)
provided by ActiveRecord associations. This method returns an instance ofActiveRecord::Associations::CollectionProxy
, which provides access to the associated records. -
The
loaded?
method checks if the association has been loaded. This ensures that the associated records are fetched only if they are already loaded, avoiding additional queries. -
The
any?
method checks if there are any associated records present. This ensures that the code block is executed only when there are associated records available. -
Finally,
first
is used to fetch the first associated record, andpublic_send(preview_url_attribute)
is used to retrieve the value of the desired attribute.
By using the association
and the methods provided by ActiveRecord associations, you can achieve the desired result in a more readable and idiomatic way without relying on send
.