This afterthought to this ancient but still relevant post
http://groups.google.com/group/rubyonrails-core/browse_thread/thread/b509a2fe2b62ac5
After realizing that after_initialize callback is a serious misnomer,
I had to figure out a way
to implement a generic solution for defaults.
Below is what I came up with.
You can simply give a defaults class method in your models. Features:
* It is also able to assign to associations
* warns against undefined assigners (typos)
* defaults can be overriden in the hash passed to the 'new'
constructor
* block given to new are correctly executed
Comments welcome
V
E.g.
class Person < ActiveRecord::Base
has_one :profile
def self.defaults
{ :profile => Profile.new, :name => 'tron' }
end
end
config/initializers/active_record_defaults.rb
class ActiveRecord::Base
# this does not work with associations...
def initialize_with_defaults(attributes=nil,&block)
defaults = self.class.respond_to?(:defaults) ?
self.class.defaults : false
initialize_without_defaults(attributes) do
if defaults then
defaults.each_pair do |a,v|
assigner_f = "#{a}="
# we force check of default attributes even if
# they are assigned already but do not override
if respond_to?(assigner_f) then
# assign value if it does not already have one
# nil is important cause value can be false!!
send(assigner_f,v) if send(a).nil?
else
raise(ArgumentError.new("unable to assign to '%s'" % a))
end
end
end
yield self if block_given?
end
end
alias_method_chain :initialize, :defaults
end
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