From: Dave Burt <dave@...>
Date: 2006-04-17T22:43:58+09:00
Subject: Re: [QUIZ] Refactoring (#75)

Hi Ruby Quiz,

Sorry, this is likely to be rather uninteresting, and I'm not even quite
following the rules, I think, but here is a refactoring that's not on
(Fowler's) official lists, even though it applies to Java as much as to
Ruby, that I did the other day; let's call them "Merge Redundant
Exception Handlers." Also, there's the more Ruby-exclusive "Remove
Unused Scope"

This code is from the Gem Server tutorial for win32/service on
RubyForge. It's by Daniel Berger, and refactored publicly without his
permission; I hope he doesn't mind.
http://rubyforge.org/docman/view.php/85/126/gemserver_tutorial.txt

   def service_main
      begin
         @s.mount_proc("/yaml") { |req, res|
            res['content-type'] = 'text/plain'
            res.body <<
Gem::Cache.from_installed_gems(File.join(Gem.dir, "specifications")).to_yaml
         }
      rescue Exception => e
         File.open(@logfile,'w+'){ |f| f.puts "Start failed: #{e}" }
         service_stop
      end

      begin
         @s.mount_proc("/") { |req, res|
            specs = []
            specifications_dir = File.join(Gem.dir, "specifications")
            Gem::Cache.from_installed_gems(specifications_dir).each do
|path, spec|
               specs << {
                  "name"           => spec.name,
                  "version"        => spec.version,
                  "full_name"      => spec.full_name,
                  "summary"        => spec.summary,
                  "rdoc_installed" =>
Gem::DocManager.new(spec).rdoc_installed?,
                  "doc_path"       => ('/doc_root/' + spec.full_name +
'/rdoc/index.html')
               }
            end
            specs = specs.sort_by { |spec| [spec["name"].downcase,
spec["version"]] }
            template = TemplatePage.new(DOC_TEMPLATE)
            res['content-type'] = 'text/html'
            template.write_html_on(res.body, {"specs" => specs})
         }
      rescue Exception => e
         File.open(@logfile,'w+'){ |f| f.puts "Start failed: #{e}" }
         service_stop
      end

      begin
         {"/gems" => "/cache/", "/doc_root" => "/doc/"}.each do
|mount_point, mount_dir|
            @s.mount(mount_point, WEBrick::HTTPServlet::FileHandler,
File.join(Gem.dir, mount_dir), true)
         end
      rescue Exception => e
         File.open(@logfile,'w+'){ |f| f.puts "Start failed: #{e}" }
         service_stop
      end

      begin
         @s.start
      rescue Exception => e
         File.open(@logfile,'w+'){ |f| f.puts "Start failed: #{e}" }
         service_stop
      end
   end


Refactoring 1: Merge Redundant Exception Handlers
/You have a series of exception handling blocks with identical handlers./
*Merge the code into a single exception handling block.*

Thus:

  begin
    foo
  rescue Exception => e
    barf e
  end
  begin
    bar
  rescue Exception => e
    barf e
  end

Becomes:

  begin
    foo
    bar
  rescue Exception => e
    barf e
  end

Refactoring 2: Remove Unused Scope
/You have a begin...end block that introduces a scope that is unused./
*Remove the unused scope.*

Thus:

  def foo
    begin
      bar
    rescue
      baz
    end
  end

Becomes:

  def foo
    bar
  rescue
    baz
  end

Here is the refactored code:

   def service_main
      @s.mount_proc("/yaml") { |req, res|
         res['content-type'] = 'text/plain'
         res.body << Gem::Cache.from_installed_gems(File.join(Gem.dir,
"specifications")).to_yaml
      }

      @s.mount_proc("/") { |req, res|
         specs = []
         specifications_dir = File.join(Gem.dir, "specifications")
         Gem::Cache.from_installed_gems(specifications_dir).each do
|path, spec|
            specs << {
               "name"           => spec.name,
               "version"        => spec.version,
               "full_name"      => spec.full_name,
               "summary"        => spec.summary,
               "rdoc_installed" =>
Gem::DocManager.new(spec).rdoc_installed?,
               "doc_path"       => ('/doc_root/' + spec.full_name +
'/rdoc/index.html')
            }
         end
         specs = specs.sort_by { |spec| [spec["name"].downcase,
spec["version"]] }
         template = TemplatePage.new(DOC_TEMPLATE)
         res['content-type'] = 'text/html'
         template.write_html_on(res.body, {"specs" => specs})
      }

      {"/gems" => "/cache/", "/doc_root" => "/doc/"}.each do
|mount_point, mount_dir|
         @s.mount(mount_point, WEBrick::HTTPServlet::FileHandler,
File.join(Gem.dir, mount_dir), true)
      end

      @s.start
   rescue Exception => e
      File.open(@logfile,'w+'){ |f| f.puts "Start failed: #{e}" }
      service_stop
   end

Cheers,
Dave