Lifecycle of HABTM related models

[Stevenwulf]

I have the following models

Installer
OperatingSystem
SupportedOperatingSystem [intersection entity]

An Installer can have many OperatingSystems, the operating systems that it supports are maintained in SupportedOperatingSystem model. It is required that and Installer be associated with at least 1 OperatingSystem.

validation code in Installer model

   def validate
 	if self.operating_systems.empty?
 	  errors.add_to_base('You must select at least one Operating System')
 	end
   end

So lets say I've created an Installer model and associated various operating systems with it. Now I want to edit the Installer model. In my form, I'm displaying all the available operating systems via checkboxes.

[x]os1 [ ]os2 [ ]os3

os1 is checked because when I created the Installer model I associated it with os1. So now I uncheck os1 and click "update." I get an error message as expected "You must select at least one Operating System." But, if I check the "supported_operating_systems" table, this association has been deleted, even though the validation failed. This is bad, because if the user decides to close their browser then the Installer model will be left in an invalid state. Is there a way to prevent this? Why is the record being deleted even though validation does not succeed?

Thanks,
Steven

[Luke Redpath]

Can you post the action that is being processed when you click "update"?

[Stevenwulf]

Here is the update action:

  
   def update
    
  	if params[:installer][:operating_system_ids].nil?
  	  params[:installer][:operating_system_ids] = []
  	end
    
  	i = @installer = Installer.find(params[:id])
  	if @installer.update_attributes(params[:installer])
  	  flash[:notice] = 'Installer was successfully updated.'
  	  redirect_to(:controller => 'software', :action => 'show', :id => i.software)
  	else
  	  self.populate_selection_values
  	  render(:action => 'edit')
  	end
    end

[MiiJaySung]

I dunno if it has anything to do with the problem or not, but I would avoid explict method defnition for validators, ather I would rename the validation method (if there are lots of validation rules I normally break them down into related methods), and then say you call you method ensure_operating_system_selected I would do something like...

validate :ensure_operating_system_selected

as a meta-method

and on an unrealted note ...

params[:installer][perating_system_ids] ||= []

can be used to eliminate the if nil statement.

If you continue to have problem, stick a raise class in the validation process and look at the stack trace, or use a breakpoint command and load up a breakpoint console to poke about and investigate the program state

[Stevenwulf]

I've actually set up my validation by defining a callback as you suggested, so I don't think that's the problem.

However, thanks for your suggestion:

params[:installer][operating_system_ids] ||= []

is much more consise.