Retrieve all association's attributes of an AR model? - ruby-on-rails

Question

What do you think is the most optimal way to retrieve all attributes for all the associations an AR model has?
i.e: let's say we have the model Target.
class Target < ActiveRecord::Base
has_many :countries
has_many :cities
has_many :towns
has_many :colleges
has_many :tags
accepts_nested_attributes_for :countries, :cities, ...
end
I'd like to retrieve all the association's attributes by calling a method on a Target instance:
target.associations_attributes
>> { :countries => { "1" => { :name => "United States", :code => "US", :id => 1 },
"2" => { :name => "Canada", :code => "CA", :id => 2 } },
:cities => { "1" => { :name => "New York", :region_id => 1, :id => 1 } },
:regions => { ... },
:colleges => { ... }, ....
}
Currently I make this work by iterating on each association, and then on each model of the association, But it's kind of expensive, How do you think I can optimize this?
Just a note: I realized you can't call target.countries_attributes on has_many associations with nested_attributes, one_to_one associations allow to call target.country_attributes

Answer 1

I'm not clear on what you mean with iterating on all associations. Are you already using reflections?
Still curious if there's a neater way, but this is what I could come up with, which more or less results in the hash you're showing in your example:
class Target < ActiveRecord::Base
has_many :tags
def associations_attributes
# Get a list of symbols of the association names in this class
association_names = self.class.reflect_on_all_associations.collect { |r| r.name }
# Fetch myself again, but include all associations
me = self.class.find self.id, :include => association_names
# Collect an array of pairs, which we can use to build the hash we want
pairs = association_names.collect do |association_name|
# Get the association object(s)
object_or_array = me.send(association_name)
# Build the single pair for this association
if object_or_array.is_a? Array
# If this is a has_many or the like, use the same array-of-pairs trick
# to build a hash of "id => attributes"
association_pairs = object_or_array.collect { |o| [o.id, o.attributes] }
[association_name, Hash[*association_pairs.flatten(1)]]
else
# has_one, belongs_to, etc.
[association_name, object_or_array.attributes]
end
end
# Build the final hash
Hash[*pairs.flatten(1)]
end
end
And here's an irb session through script/console to show how it works. First, some environment:
>> t = Target.create! :name => 'foobar'
=> #<Target id: 1, name: "foobar">
>> t.tags.create! :name => 'blueish'
=> #<Tag id: 1, name: "blueish", target_id: 1>
>> t.tags.create! :name => 'friendly'
=> #<Tag id: 2, name: "friendly", target_id: 1>
>> t.tags
=> [#<Tag id: 1, name: "blueish", target_id: 1>, #<Tag id: 2, name: "friendly", target_id: 1>]
And here's the output from the new method:
>> t.associations_attributes
=> {:tags=>{1=>{"id"=>1, "name"=>"blueish", "target_id"=>1}, 2=>{"id"=>2, "name"=>"friendly", "target_id"=>1}}}

Answer 2

try this with exception handling:
class Target < ActiveRecord::Base
def associations_attributes
tmp = {}
self.class.reflections.symbolize_keys.keys.each do |key|
begin
data = self.send(key) || {}
if data.is_a?(ActiveRecord::Base)
tmp[key] = data.attributes.symbolize_keys!
else
mapped_data = data.map { |item| item.attributes.symbolize_keys! }
tmp[key] = mapped_data.each_with_index.to_h.invert
end
rescue Exception => e
tmp[key] = e.message
end
end
tmp
end
end

Answer 3

This is updated version of Stéphan Kochen's code for Rails 4.2
def associations_attributes
association_names = self.class.reflect_on_all_associations.collect { |r| r.name }
me = self.class.includes(association_names).find self.id
pairs = association_names.collect do |association_name|
object_or_array = me.send(association_name)
if object_or_array.is_a? ActiveRecord::Associations::CollectionProxy
association_pairs = object_or_array.collect { |o| [o.id, o.attributes] }
[association_name, Hash[*association_pairs.flatten(1)]]
else
[association_name, object_or_array.attributes]
end
end
Hash[*pairs.flatten(1)]
end