Is there a way to list all belongs_to associations?

Question

I need to list all belongs_to associations in a model object and iterate through them. Is there a way to do this?

Answer 1

Thing.reflections.collect{|a, b| b.class_name if b.macro==:belongs_to}.compact 
#=> ["Foo", "Bar"]

of course, you can pass :has_many, or any other associations too

Answer 2

You can make use of reflect_on_all_associations method from Reflection For example:

Thing.reflect_on_all_associations(:belongs_to)

Answer 3

You could make use of the class's reflections hash to do this. There may be more straightforward ways, but this works:

# say you have a class Thing
class Thing < ActiveRecord::Base
  belongs_to :foo
  belongs_to :bar
end

# this would return a hash of all `belongs_to` reflections, in this case:
# { :foo => (the Foo Reflection), :bar => (the Bar Reflection) }
reflections = Thing.reflections.select do |association_name, reflection| 
  reflection.macro == :belongs_to
end

# And you could iterate over it, using the data in the reflection object, 
# or just the key.
#
# These should be equivalent:
thing = Thing.first
reflections.keys.map {|association_name| thing.send(association_name) }
reflections.values.map {|reflection| thing.send(reflection.name) }