How the plugin works

1) remember all the attributes that are supplied to new
ex. Product.new(:name => “bla”, :price => “€5″)
default_value_for will remember that the name and the price are set.

2) the new product attributes will be overwritten with the default values except for price and name

problem case:

class Product
default_values {:price => “5″, :currency => “$”}
def price= price_and_currency
self.price = separate_price_form_price_and_currency(price_and_currency)
self.currency = separate_currency_form_price_and_currency(price_and_currency)
end
end

Product.new(:name => “bla”, :price => “€6″)
attributes are correctly set and not touched by the plugin
1) :name => “bla”, :price => “€6″, :currency => “€”
Then the plugin overwrites attributes with default values except for :price
BUT it will not check on custom setters which alter other attributes
2) :name => “bla”, :price => “€6″, currency => “$”
Our ‘€’ got overwritten by the default value of ‘$’

class Student < ActiveRecord::Base
has_many :klasses

def after_initialize
klasses.build(:student_id => id, :status => “registered”)
end
end

@student = Student.new
@student.klasses # <– klass id: nil, student_id: 1, status: registered

thus automatically building the klasses association right when a new student is created. Unfortunately after_initialize is also called on find which causes problems. Thus the need for a workaround.

Ya I know its a strange example. Sorry again. No preview.

Does it works with nested attributes?

I’m having problem with this:

class Person ...)

the problem is that p.category now returns the default value.

I’m having problem with this:

class Person …)

the problem is that p.category now returns the default value.

++ for core addition.

Sorry the beginning did not come out correctly:

It should have shown this:

I use default_value in my model for students to set some inheritance:
class Student < ActiveRecord::Base

belongs_to :user
belongs_to :klass

# Create programatic default values for each element in the database
default_value_for :user_id do current_user.id end
default_value_for :last_name do current_user.last_name end
default_value_for :address do current_user.address end
default_value_for :city do current_user.city end
default_value_for :zip do current_user.zip end
default_value_for :home_phone do current_user.home_phone end

default_value_for has worked fine for me under Rails 2.2.2 in Production and Development, but it fails under Rails 2.3

In Development mode it fails when the student model (per above) is used. Error message is:
(as shown in previous post)

In Production mode it prevents Mongrel from starting up. The Mongrel bootup log is shown in the previous post.

Sorry for the edit mixup

I use default_value in my model for students to set some inheritance:
class Student “3c03f9d9352d163861e6ba703f1e633a”, “action”=>”new”, “_method”=>”get”, “adapter”=>”_list_inline_adapter”, “controller”=>”student”}

SystemStackError (stack level too deep):
app/models/student.rb:7
vendor/plugins/default_value_for/init.rb:38:in `call’
vendor/plugins/default_value_for/init.rb:38:in `evaluate’
vendor/plugins/default_value_for/init.rb:81:in `initialize’
vendor/plugins/default_value_for/init.rb:79:in `initialize’
vendor/plugins/default_value_for/init.rb:71:in `initialize’
app/controllers/student_controller.rb:7

Rendered rescues/_trace (27.2ms)
Rendered rescues/_request_and_response (1.2ms)

Mongrel Bootup in Production mode:
=> Booting Mongrel
=> Rails 2.3.2 application starting on http://0.0.0.0:3000
/rails/formdir-dev/app/models/student.rb:7: warning: Object#id will be deprecated; use Object#object_id
/usr/lib64/ruby/gems/1.8/gems/activesupport-2.3.2/lib/active_support/dependencies.rb:443:in `load_missing_constant’: uninitialized constant Logging (NameError)
from /usr/lib64/ruby/gems/1.8/gems/activesupport-2.3.2/lib/active_support/dependencies.rb:80:in `const_missing’
from /usr/lib64/ruby/gems/1.8/gems/activesupport-2.3.2/lib/active_support/dependencies.rb:92:in `const_missing’
from /usr/lib64/ruby/gems/1.8/gems/logging-1.1.2/lib/logging.rb:479
from /usr/lib64/ruby/site_ruby/1.8/rubygems/custom_require.rb:32
/rails/formdir-dev/app/models/student.rb:8: undefined method `last_name’ for nil:NilClass (NoMethodError)
from /rails/formdir-dev/vendor/plugins/default_value_for/init.rb:38:in `call’
from /rails/formdir-dev/vendor/plugins/default_value_for/init.rb:38:in `evaluate’
from /rails/formdir-dev/vendor/plugins/default_value_for/init.rb:81:in `initialize’
from /usr/lib64/ruby/gems/1.8/gems/activesupport-2.3.2/lib/active_support/ordered_hash.rb:69:in `each’
from /usr/lib64/ruby/gems/1.8/gems/activesupport-2.3.2/lib/active_support/ordered_hash.rb:69:in `each’
from /rails/formdir-dev/vendor/plugins/default_value_for/init.rb:79:in `initialize’
from /usr/lib64/ruby/gems/1.8/gems/activerecord-2.3.2/lib/active_record/base.rb:2441:in `initialize_without_defaults’
from /rails/formdir-dev/vendor/plugins/default_value_for/init.rb:71:in `initialize’
… 22 levels…
from /usr/lib64/ruby/gems/1.8/gems/rails-2.3.2/lib/commands/server.rb:84
from /usr/lib64/ruby/site_ruby/1.8/rubygems/custom_require.rb:31:in `gem_original_require’
from /usr/lib64/ruby/site_ruby/1.8/rubygems/custom_require.rb:31:in `require’
from script/server:3

default_value_for :foo, {}

…then the same hash is shared between instances. Perhaps a call to duping the default would work: in the mean time I am using the block form of default_value_for.

UUIDs look like this: 343e50b4-ba44-11dd-beb2-001ec2186a45

And they’re not just a random number. I wrote a Ruby library awhile back for generating real UUIDs, and it’s probably worth using, since it really does give you true uniqueness. Plus it runs on Ruby 1.8.x, 1.9.x, and JRuby.

http://uuidtools.rubyforge.org/api/

Your code above would become:


require "uuidtools"
class User "ee0ec316-ba44-11dd-beb2-001ec2186a45"
User.new.uuid # => "ee79dc32-ba44-11dd-beb2-001ec2186a45"


super_market = SuperMarket.create(:name => ‘Albert Zwijn’, :default_price => 100)
soap = super_market.products.build(:super_market => super_market, :name => ‘Soap’)
soap.price # => 100