Remember your MVCs
Cross posted from Giant Robots
From novice to expert, I’m sure every Rails developer believes in MVC. But all to often I’ve seen programmers cut right through the Model/View/Controller boundaries when implementing new features – especially where precedent hasn’t yet been set.
I can understand where the urge comes from, as there are times when the boundaries are fuzzy. Rails has the
validates_confirmation_of for entering a password and a password confirmation, while a good argument could be made that this is logic that should never be in the model. If the record was created by a 3rd party application, then it shouldn’t have to specify the password twice in the XML just because the model is usually used by humans. And the writers of the macro acknowledge this by not having it kicking in if the field is nil.
attr_accessor :other_primary_source_of_funding attr_accessor :other_heard_through before_save :replace_with_others def replace_with_others unless other_primary_source_of_funding.blank? self.primary_source_of_funding = other_primary_source_of_funding end unless other_heard_through.blank? self.heard_through = other_heard_through end end
This code wins points in being concise and understandable, but is also a big ’ol MVC violation. The “Right” solution is to grab the value in the controller:
before_filter :convert_combobox_values, :only => [:create, :update] def convert_combobox_values if params[:object][:primary_source_of_funding] == "Other" params[:object][:primary_source_of_funding] = params[:object].delete(:other_primary_source_of_funding) end if params[:object][:heard_through] == "Other" params[:object][:heard_through] = params[:object].delete(:other_heard_through) end end
Here’s the question you should be asking yourself when you think you’re treading the MVC line: “Would the model need this method if it wasn’t being accessed through HTML?” If you were using this model in a desktop application, that question for the example above would be No.
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