Uninitialized Constant Error when catching Exception

I need to post articles to Wordpress via XMLRPC and catch any exceptions:

connection = XMLRPC::Client.new('mysite.com', '/xmlrpc.php', 80)
  connection.call(
  'metaWeblog.newPost',
  1,
  'user',
  'password',
  post,
  true
)

There is en error:

C:/Ruby192/lib/ruby/1.9.1/rexml/parsers/baseparser.rb:441:in `rescue in pull': #<NoMethodError: undefined method `[]' for nil:NilClass> (REXML::ParseException)
C:/Ruby192/lib/ruby/1.9.1/rexml/parsers/baseparser.rb:341:in `pull'
C:/Ruby192/lib/ruby/1.9.1/rexml/parsers/streamparser.rb:16:in `parse'
C:/Ruby192/lib/ruby/1.9.1/rexml/document.rb:204:in `parse_stream'
C:/Ruby192/lib/ruby/1.9.1/xmlrpc/parser.rb:717:in `parse'
C:/Ruby192/lib/ruby/1.9.1/xmlrpc/parser.rb:460:in `parseMethodResponse'
C:/Ruby192/lib/ruby/1.9.1/xmlrpc/client.rb:421:in `call2'
C:/Ruby192/lib/ruby/1.9.1/xmlrpc/client.rb:410:in `call'

I successfully caught the exception with:

connection = XMLRPC::Client.new('mysite.com', '/xmlrpc.php', 80)
beg开发者_C百科in
  connection.call(
    'metaWeblog.newPost',
    1,
    'user',
    'password',
    post,
    true
  )
rescue REXML::ParseException
  puts "Skipping error"
end

Post is OK, article is in Wordpress.

Next I needed to catch an exception about site availability (when site is not accessible) I tried to catch the exception with:

connection = XMLRPC::Client.new('notaccessibleSite.com', '/xmlrpc.php', 80)
begin
  connection.call(
    'metaWeblog.newPost',
    1,
    'user',
    'password',
    post,
    true
  )
rescue REXML::ParseException
  puts "Skipping error"
rescue
  puts "Others errors"
end

But this does not work:

myscript.rb:47:in `rescue in makeRpc': uninitialized constant Object::REXML (NameError)
from myscript.rb:38:in `makeRpc'
from myscript.rb:62:in `block in postContent'
from myscript.rb:58:in `each'
from myscript.rb:58:in `postContent'
from myscript.rb:71:in `<top (required)>'
from -e:1:in `load'
from -e:1:in `<main>'

Any suggestions?

Have you tried require 'rexml/document'. Have a look at the documentation for rexml/document.rb. It requires 'rexml/rexml' for you as well as 'rexml/parseexception'.

The following doesn't produce any errors:

require "rexml/document"

begin
    doc = REXML::Document.new File.new('blah.txt')
rescue REXML::ParseException => msg
    puts "Failed: #{msg}"
end

However if you replace the rexml/document with 'rexml/rexml', you get:

blah.rb:22:in `rescue in <main>': uninitialized constant REXML::ParseException (NameError)
    from abc.rb:20:in `<main>'

Update (based on comments):

If you want to check that REXML::ParseException is defined, something like the following will work:

if defined?(REXML::ParseException) == 'constant' && REXML::ParseException.class == Class  
  puts "REXML::ParseException is defined"
else
  puts "REXML::ParseException is NOT defined" 
end

Seems that it can't find Object::REXML when you are testing this case, maybe a rescue NameError rescues this.

You must require 'rexml/rexml' before.