[LRUG] Query about ActiveRecord

[John Winters]

I'm still plodding along learning about Rails and I've got a query about 
ActiveRecord.  I think I've explained to myself what's happening (but 
want to check that I've got it right) and I'm wondering whether there's 
a better way of doing what I want to do.

I have a model called a cycle, and it has an attribute called a pattern. 
  It's just a string which the user enters and it's meant to be a fixed 
length.  If the user enters too short a string I want to pad it out to 
the required length before it's saved to the database.  The way I tried 
to do it was by writing my own accessor functions like this:

class Cycle < ActiveRecord::Base

   def pattern
     @pattern
   end

   def pattern=(new_pattern)
     #
     # Pad new_pattern to required length if needed, and then...
     #
     @pattern = new_pattern
   end

end

Obviously you have to use @pattern and not self.pattern or you end up 
with a recursive call.

This ran OK, but the new value was not saved to the database.  I'm 
assuming I've broken things by writing my own accessor functions for a 
database column item.  Perhaps ActiveRecord doesn't realise the instance 
variable has been updated?  The way I've worked around it is to do:

class Cycle < ActiveRecord::Base

   def mpattern
     self.pattern
   end

   def mpattern=(new_pattern)
     #
     # Pad new_pattern to required length if needed, and then...
     #
     self.pattern = new_pattern
   end

end

and then change the name of the field in the view from "pattern" to 
"mpattern".  This works, but strikes me as messy.  Is there a more 
rails-correct way of doing it?

TIA,
John