Question

For conditional validation in Rails, I can do this:

mailed_or_faxed_agenda = Proc.new { |me| me[:agenda_mailed_faxed] }
validates_presence_of :agenda, :if=>!mailed_or_faxed_agenda

but I don’t know how to parameterize the Proc. I would love to use if=>blah(name) but I cannot figure out how to it. Any ideas?

Note: In these ifs one can also use the name of a method, but as a symbol. I can’t imagine how to pass parameters to that.

Answer 1

By “parameterize the Proc”, do you mean currying?

Or just this?

my_proc = Proc.new { |chunky| do stuff to 'chunky' here }

my_proc.call("bacon") # "bacon" is "chunky" in the above proc

The second problem (sending params to a method), you can do something like this:

validates_presence_of :some_column_name
  :if => Proc.new { |model_instance| model_instance.send(:some_method, arg1, arg2, arg3) }

Update:

The above can be simplified if you don’t want to parameterize the method that is called. The following is equivalent to passing a literal symbol to send:

validates_presence_of :some_column_name
  :if => Proc.new { |model_instance| model_instance.some_method(arg1, arg2, arg3) }