Rails has_many with dynamic conditions

model, ruby-on-rails

Solution

Rails 4+ way (Thanks to Thomas who answered this below):

has_many :faixas_aliquotas, -> (object) { 
           where("regra_fiscal = ?", object.regra_fiscal)
         },
         :class_name => 'Fiscal::FaixaAliquota'

Rails 3.1+ way:

has_many :faixas_aliquotas, :class_name => 'Fiscal::FaixaAliquota',
         :conditions => proc { "regra_fiscal = #{self.regra_fiscal}" }

Rails 3 and below:

has_many :faixas_aliquotas, :class_name => 'Fiscal::FaixaAliquota',
         :conditions => ['regra_fiscal = #{self.regra_fiscal}']

No. This is not a mistake. The conditions are specified in single quotes and still contains the code `#{self.regra_fiscal}`. When the conditions clause is evaulated, the regra_fiscal method will be called on the object of `self` (whatever the class is). Putting double quotes will not work.

I hope this is what you are looking for.

Problem

What I want is to create a Model that connects with another using a has_many association in a dynamic way, without the foreign key like this: ``` has_many :faixas_aliquotas, :class_name => 'Fiscal::FaixaAliquota', :conditions => ["regra_fiscal = ?", ( lambda { return self.regra_fiscal } ) ] ``` But I get the error: ``` : SELECT * FROM "fis_faixa_aliquota" WHERE ("fis_faixa_aliquota".situacao_fiscal_id = 1 AND (regra_fiscal = E'--- !ruby/object:Proc {}')) ``` Is this possible?

Original source