创建实例时初始化一个哈希变量

Question

我试图初始化一个类变量作为哈希当我创建一个SomeClass的实例但我不断收到错误。有点新红宝石，所以任何帮助，将不胜感激。感谢

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

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

NoMethodError：未定义的方法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:in method_missing的”
从/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:in检查 '
从/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:in检查'
从的/ opt/local/lib目录/ruby/1.8/irb.rb:310:in output_value'
from /opt/local/lib/ruby/1.8/irb.rb:159:in eval_input'
from /opt/local/lib/ruby/1.8/irb.rb:271:in signal_status'
from /opt/local/lib/ruby/1.8/irb.rb:155:in eval_input'
从/opt/local/lib/ruby/1.8/irb.rb:154:in eval_input'
from /opt/local/lib/ruby/1.8/irb.rb:71:in开始从
'从/opt/local/lib/ruby/1.8/irb.rb:70:in catch'
from /opt/local/lib/ruby/1.8/irb.rb:70:in开始
'/opt/local/bin/irb：13

Answer 1

This article should help you。

在Ruby中，你可以很容易地覆盖通过简单地重新定义方法（“猴子补丁”）

这是#initialize方法，你在写现有的从宝石代码：

# 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