Initializing a hash variable when creating an instance

Question

I am trying to initialize a class variable as a hash when I create an instance of SomeClass but I keep getting an error. Somewhat new to ruby so any help would be appreciated. Thanks

class SomeClass < ActiveRecord::Base  
  attr_accessible :some_hash  
  serialize :some_hash,   Hash  

  def initialize(args = {})  
    @some_hash != {}  
  end  
end

NoMethodError: undefined method has_key?' for nil:NilClass from /opt/local/lib/ruby/gems/1.8/gems/activesupport-2.3.8/lib/active_support/whiny_nil.rb:52:inmethod_missing'
from /opt/local/lib/ruby/gems/1.8/gems/activerecord-2.3.8/lib/active_record/base.rb:2827:in has_attribute?' from /opt/local/lib/ruby/gems/1.8/gems/activerecord-2.3.8/lib/active_record/base.rb:2888:ininspect'
from /opt/local/lib/ruby/gems/1.8/gems/activerecord-2.3.8/lib/active_record/base.rb:2887:in collect' from /opt/local/lib/ruby/gems/1.8/gems/activerecord-2.3.8/lib/active_record/base.rb:2887:ininspect'
from /opt/local/lib/ruby/1.8/irb.rb:310:in output_value' from /opt/local/lib/ruby/1.8/irb.rb:159:ineval_input'
from /opt/local/lib/ruby/1.8/irb.rb:271:in signal_status' from /opt/local/lib/ruby/1.8/irb.rb:155:ineval_input'
from /opt/local/lib/ruby/1.8/irb.rb:154:in eval_input' from /opt/local/lib/ruby/1.8/irb.rb:71:instart'
from /opt/local/lib/ruby/1.8/irb.rb:70:in catch' from /opt/local/lib/ruby/1.8/irb.rb:70:instart'
from /opt/local/bin/irb:13

monocle · Accepted Answer · 2010-12-06 14:37:20Z

2

This article should help you.

In Ruby, you can easily overwrite existing code from gems by simply redefining the method ("monkey patching")

This is the #initialize method you over wrote:

# active_record/base.rb
  def initialize(attributes = nil)
    @attributes = attributes_from_column_definition
    @attributes_cache = {}
    @new_record = true
    @readonly = false
    @destroyed = false
    @marked_for_destruction = false
    @previously_changed = {}
    @changed_attributes = {}

    ensure_proper_type

    populate_with_current_scope_attributes
    self.attributes = attributes unless attributes.nil?

    result = yield self if block_given?
    _run_initialize_callbacks
    result
  end

answered Dec 6, 2010 at 14:37

monocle

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