Run All Validations Except Any of "kind" :presence - ruby-on-rails

Question

Is there a way to run only validations of a specific type?
I have an application that updates multiple class instances in a single form. Validations are performed by creating an instance of building and validating on that.
The problem: if an attribute isn't being updated, the form field is left blank and the form submits an empty string. You can see an example here where params[:building][:name] is an empty string.
params = {:building=>{:name=>"", :short_name=>"", :code=>"test"}, :commit=>"Update Buildings", :building_ids=>["2", "5", "7"], :action=>"update_multiple", :controller=>"buildings"}
How can I run all the validations excluding those that check for the presence of an attribute?
def update_multiple
#building = Building.new(params[:building].reject {|k,v| v.blank?})
respond_to do |format|
if #building.valid?
Building.update_all( params[:building].reject {|k,v| v.blank?}, {:id => params[:building_ids]} )
format.html { redirect_to buildings_path, notice: 'Buildings successfully updated.' }
else
#buildings = Building.all
format.html { render action: 'edit_multiple' }
end
end
end
I've spent quite a bit of time working on this, and here's what I've found so far:
To retrieve a models validations
$ Building.validators
=> [#<ActiveModel::Validations::PresenceValidator:0x007fbdf4d6f0b0 #attributes=[:name], #options={}>]
To get a validators kind
$ Building.validators[0].kind
=> :presence
This is the method used by rails to run validations:
https://github.com/rails/rails/blob/master/activesupport/lib/active_support/callbacks.rb
line 353
# This method runs callback chain for the given kind.
# If this called first time it creates a new callback method for the kind.
# This generated method plays caching role.
#
def __run_callbacks(kind, object, &blk) #:nodoc:
name = __callback_runner_name(kind)
unless object.respond_to?(name, true)
str = object.send("_#{kind}_callbacks").compile
class_eval <<-RUBY_EVAL, __FILE__, __LINE__ + 1
def #{name}() #{str} end
protected :#{name}
RUBY_EVAL
end
object.send(name, &blk)
end
If there is a way to run validations directly? If so, I could iterate over the Building.validators and only run those with kind != :presence.
I'd love to hear any ideas you have.

Answer 1

I think circumventing specific validations is an interesting idea, but I think there's an easier way. I'd handle this by writing a custom method that validates batch updates, something like this:
def valid_for_batch?(params)
#building = Building.new(params[:building].reject {|k,v| v.blank?})
#building.name = "Foo" if #building.name.blank?
#building.shortname = "Bar" if #building.shortname.blank?
# etc...
#building.valid?
end
Just make sure that "Foo" and "Bar" up there are values that will pass your validation - all that code is doing is looking to see if the values are empty and if so, replacing them with a temporary value that will pass validation. That way, the only way that #building.valid? will return false at the end is if there were existing bad data.

Answer 2

Wow, after working on this issue for many hours, it looks to be a very difficult problem.
Create a class instance #building and set placeholders for attributes whose presence is validated.
I've tried many different approaches and this is the best I can come up with so far.
def update_multiple
valid = true
#building = Building.new(params[:building])
set_bulk_edit_placeholders_for_presence_validators(#building)
building_valid = #building.valid?
# Check if buildings were selected to edit
if params[:building_ids].blank?
valid = false
#building.errors.add(:base, 'You must select at least one Building')
end
# Check if all form fields are blank
if params[:building].values.delete_if {|v| v.blank?}.blank?
valid = false
#building.errors.add(:base, 'The edit form must not be empty')
end
respond_to do |format|
if valid && building_valid
#buildings = Building.find(params[:building_ids])
#buildings.each do |building|
building.update_attributes!(params[:building].reject { |k,v| v.blank? })
end
format.html { redirect_to buildings_path, notice: 'Buildings were successfully updated.' }
else
#buildings = Building.all
format.html { render edit_multiple_buildings_path }
end
end
end
This is a general function to set the placeholders. It can be used for any model from any controller.
application_controller.rb
private
def set_bulk_edit_placeholders_for_presence_validators(class_instance, hash={})
model_name = hash[:model_name] || self.class.name.sub("Controller", "").singularize.downcase
klass = self.class.name.sub("Controller", "").singularize.constantize
klass.send(:validators).each { |validator|
if (validator.kind == :presence)
validator.attributes.each { |attribute|
if params[model_name][attribute].blank?
class_instance.send("#{attribute}=", 'placeholder')
end
}
end
}
end
In order to display the errors properly on the form it has to be a form_for #buildings.
Since the placeholders are set for the #buildings object, we have to specify that the form values come directly from params.
edit_multiple.haml
= bootstrap_form_for #building, :url => update_multiple_buildings_path, :method => :put, :html => {:class => 'form-horizontal'} do |f|
= f.text_field :name, :value => params[:building].try(:send, :[], :name)
= f.text_field :short_name, :value => params[:building].try(:send, :[], :short_name)
= f.text_field :code, :value => params[:building].try(:send, :[], :code)
= f.submit 'Update Buildings', :name => nil
%table.table.table-striped.table-bordered
%thead
%tr
%th.check_box_column= check_box_tag 'select_all'
%th.sortable= sortable :name
%th Abbr Name
%th.sortable= sortable :code
%th
%tbody
- #buildings.each do |building|
%tr
%td.check_box_column= check_box_tag 'building_ids[]', building.id, (params[:building_ids].include?(building.id.to_s) if params[:building_ids])
%td= building.name
%td= building.short_name
%td= building.code
%td.links.span2
= link_to 'Show', building
= link_to 'Edit', edit_building_path(building)
= link_to 'Delete', building, :method => :delete, :confirm => 'Are you sure you want to delete this building?'
I hope this can be of help to others working on similar "bulk update" validation issues.