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POWhat is the difference between "__send__" and "instance_variable_get / instance_variable_set" methods?
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  1. POWhat is the difference between "__send__" and "instance_variable_get / instance_variable_set" methods?
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    copied!<p>All is stated in the question. Both of these methods can access (read/write) instance variables by using their code name :</p> <pre><code>__send__ instance_variable_set instance_variable_get </code></pre> <p>Could someone explain it by examples ?</p> <p>Metaprogramming is sometimes melting our brain when we explore it with abstraction.</p> <p>=== EDIT ===</p> <p>Ok I make a resume of the answers as an example for later use if my brain is melting again.</p> <p><strong>Class declaration</strong> :</p> <pre><code>class Person attr_accessor :first_name, :last_name def initialize(first_name, last_name) @first_name = first_name @last_name = last_name end def full_name @first_name + ' ' + @last_name end end </code></pre> <p><strong>Initialization</strong> :</p> <pre><code>actor = Person.new('Donald', "Duck") =&gt; #&lt;Person:0xa245554 @first_name="Donald", @last_name="Duck"&gt; </code></pre> <p><strong>usage of send</strong> (read) :</p> <pre><code>actor.send('first_name') =&gt; "Donald" actor.send(:first_name) =&gt; "Donald" actor.send("last_name") =&gt; "Duck" actor.send(:last_name) =&gt; "Duck" actor.send('full_name') =&gt; "Donald Duck" actor.send(:full_name) =&gt; "Donald Duck" </code></pre> <p><strong>usage of instance_variable_get</strong> (read)</p> <pre><code>actor.instance_variable_get('@first_name') =&gt; "Donald" actor.instance_variable_get(:@first_name) =&gt; "Donald" actor.instance_variable_get('@last_name') =&gt; "Duck" actor.instance_variable_get(:@last_name) =&gt; "Duck" </code></pre> <p><strong>usage of send</strong> (write) :</p> <pre><code>actor.send('first_name=', 'Daisy') actor.send('full_name') =&gt; "Daisy Duck" actor.send(:first_name=, "Fifi") actor.send("full_name") =&gt; "Fifi Duck" </code></pre> <p><strong>usage of instance_variable_set</strong> (write)</p> <pre><code>actor.instance_variable_set('@first_name', 'Pluto') actor.send("full_name") =&gt; "Pluto Duck" actor.instance_variable_set(:@last_name, 'Dog') actor.send(:full_name) =&gt; "Pluto Dog" </code></pre> <p><strong>INCORRECT usage of instance_variable_get</strong> (read)</p> <pre><code>actor.instance_variable_get('full_name') #NameError: `full_name' is not allowed as an instance variable name actor.instance_variable_get('last_name') #NameError: `last_name' is not allowed as an instance variable name </code></pre> <p>I was geting confuse with Rails ActiveRecord and its Associations.</p> <p>Thanks for the answers !</p>
 

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