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POHow do I dynamically update an instance array to hold a list of dynamic methods on instantiation?
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  1. POHow do I dynamically update an instance array to hold a list of dynamic methods on instantiation?
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    copied!<p>I am trying to dynamically define methods based on xml mappings. This works really well. However I want to create an instance variable that is a array of the dynamically defined methods.</p> <p>My code looks something like this</p> <pre><code> def xml_attr_reader(*args) xml_list = "" args.each do |arg| string_val = "def #{arg}; " + " xml_mapping.#{arg}; " + "end; " self.class_eval string_val xml_hash = xml_list + "'#{arg}'," end self.class_eval "@xml_attributes = [] if @xml_attributes.nil?;" + "@xml_attributes = @xml_attributes + [#{xml_list}];" + "puts 'xml_attrs = ' + @xml_attributes.to_s;" + "def xml_attributes;" + " puts 'xml_attrs = ' + @xml_attributes.to_s;" + " @xml_attributes;" + "end" end </code></pre> <p>So everything works except when I call xml_attributes on an instance it return null (and prints out 'xml_attrs = ').</p> <p>While the puts before the definition actually prints out the correct array. (when I instantiate the instance)</p> <p><hr> Update - <a href="https://stackoverflow.com/users/163203/kandadaboggu">kandadaboggu</a> solution below works. I really did not explain my question fully though so here is more information. I want to call xml_attr_reader within a class that extends XmlConfig. Basically I want it to work in the same way as attr_reader of active record.</p> <p>Taking <a href="https://stackoverflow.com/users/163203/kandadaboggu">kandadaboggu</a> solution of </p> <pre><code>class XmlConfig def xml_attr_reader(*args) args.each do |arg| class_eval(&lt;&lt;-RUBY, __FILE__, __LINE__) def #{arg} xml_mapping.#{arg} end RUBY end unless respond_to?(:xml_attributes) class_eval(&lt;&lt;-RUBY, __FILE__, __LINE__) attr_accessor :xml_attributes RUBY end (self.xml_attributes ||=[]).concat(args) end end </code></pre> <p>and</p> <pre><code>config = XmlConfig.new config.xml_attr_reader("age", "name") config.age #=&gt; age config.name #=&gt; name config.xml_attributes #=&gt; ["age", "name" ] config.xml_attr_reader("city") config.city #=&gt; city config.xml_attributes #=&gt; ["age", "name", "city"] </code></pre> <p>What I really want is this (where I had XmlConfig as a module not a Class in my version though)</p> <pre><code>class Event &lt; ActiveWhatever extend XmlConfig xml_attr_reader :age, :name xml_attr_reader :email, :location end class PrivateEvent &lt; Event xml_attr_reader :owner, :password end </code></pre>
 

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