Calling method from string in Ruby

A week and a little bit has passed since the beginning of coding for Google Summer of Code 2009. I am getting more and more excited since I am learning more of advanced Ruby programming.

So I am parsing XML into objects using LibXML::XML::Reader. I had this code:

 1     def parse_events()
 2       events = Events.new
 3       @reader.read #go to next element
 4       #read while have reached end of events
 5       while not(is_end_element?('events')) do
 6         if is_element?('type')
 7           @reader.read
 8           events.type = @reader.value
 9           @reader.read
10           has_reached_end_tag?('type')
11         end
12         if is_element?('duplications')
13           @reader.read
14           events.duplications = @reader.value.to_i
15           @reader.read
16           has_reached_end_tag?('duplications')
17         end
18         if is_element?('speciations')
19           @reader.read
20           events.speciations = @reader.value.to_i
21           @reader.read
22           has_reached_end_tag?('speciations')
23         end
24         if is_element?('losses')
25           @reader.read
26           events.losses = @reader.value.to_i
27           @reader.read
28           has_reached_end_tag?('losses')
29         end
30         if is_element?('confidence')
31           events.confidence = parse_confidence
32         end
33         @reader.read
34       end
35       return events
36     end #parse_events

This was too much of code duplication, but the problem was that each time different method of the events object is called.

After some searching on interwebs, luckily, I found out that ruby has a method send, which invokes the method identified by symbol and passes any arguments.

So I created such method:

  def parse_simple_element(object, name)
    if is_element?(name)
      @reader.read
      object.send("#{name}=", @reader.value)
      @reader.read
      has_reached_end_tag?(name)
    end
  end

So now the method parse_events() can be rewritten like this:

   def parse_events()
     events = Events.new
     @reader.read #go to next element
     while not(is_end_element?('events')) do
       ['type', 'duplications', 'speciations', 'losses'].each { |elmt|
         parse_simple_element(events, elmt)
       }
       if is_element?('confidence')
         events.confidence = parse_confidence
       end
       @reader.read
     end
     return events
   end #parse_events

Much shorter!! Now I run the unit tests and it works! No worries that I broke something while refactoring code. In cases like this I really appreciate the power of unit testing.