My Rails Antipattern!

Use has_many through

Suppose that we have the following models.

class AClass  < ActiveRecord::Base
  has_many :b_classes  
end

class BClass  < ActiveRecord::Base
  has_many :c_classes  
end

class CClass  < ActiveRecord::Base
  belongs_to :bclass
end

Then, I wrote the following codes.

a = AClass.find(10)
a.b_classes.eahc do |b|
  b.c_classes.each do |c|
    puts c
  end
end

The above code could wrriten like the following.

class AClass  < ActiveRecord::Base
  has_many :b_classes  
  has_many :b_classes_c_classes, through: :b_classes, source: :c_classes
end

class BClass  < ActiveRecord::Base
  has_many :c_classes  
end

class CClass  < ActiveRecord::Base
  belongs_to :bclass
end

Now a record of AClass directly access to c_classes of each b_class. Notice that the record of b_classes_c_classes may include the same record. In this case we can use distinct to get records uniquely.

a = AClass.find(10)
a.b_classes_c_classes.distinct.each do |c|
  puts c
end

Written on December 1, 2017