REXML and new file problem? bug?

ruby-talk
1

Hello,

I want to use the REXML class, but encounter the following problem, if I want to use an un-existant file:

file = File.new( "mydoc2.xml", "w+" ) # and this document does not exist
xml = Document.new(file)

I get the following error:

C:/ruby/lib/ruby/1.8/rexml/source.rb:128:in `initialize': undefined method `[]' for nil:NilClass (NoMethodError)
    from C:/ruby/lib/ruby/1.8/rexml/parsers/baseparser.rb:126:in `new'
    from C:/ruby/lib/ruby/1.8/rexml/parsers/baseparser.rb:126:in `stream='
    from C:/ruby/lib/ruby/1.8/rexml/parsers/baseparser.rb:100:in `initialize'
    from C:/ruby/lib/ruby/1.8/rexml/parsers/treeparser.rb:8:in `new'
    from C:/ruby/lib/ruby/1.8/rexml/parsers/treeparser.rb:8:in `initialize'
    from C:/ruby/lib/ruby/1.8/rexml/document.rb:177:in `new'
    from C:/ruby/lib/ruby/1.8/rexml/document.rb:177:in `build'
    from C:/ruby/lib/ruby/1.8/rexml/document.rb:45:in `initialize'
    from C:/Documents and Settings/Bart/My Documents/Programming/Ruby/Examples/XML/XMLTest1.rb:12:in `new'
    from C:/Documents and Settings/Bart/My Documents/Programming/Ruby/Examples/XML/XMLTest1.rb:12

So I put on my 'gutty' shoes, and have a look, and saw that in the file C:/ruby/lib/ruby/1.8/rexml/source.rb, around 128, there is:
      str = @source.read( 2 )
      puts str, @source
      if (str[0] == 254 && str[1] == 255) || (str[0] == 255 && str[1] == 254)

However, as @source is an empty file (I know this because of the puts), I get a nill as str, and hence, that error.

There are work-arounds for this (write to String and then to file), or maybe Im not supposed to do this, but it looked un-Ruby, at first. If the file is new, it should not try to parse it.

Just to let you know,

Bart.

2

This is not a bug, from the documentation on the constructor:

"Constructor @param source if supplied, must be a Document, String, or IO. Documents have their context and Element attributes cloned. Strings are expected to be valid XML documents. IOs are expected to be sources of valid XML documents"
^^^^^^^^^^^^^^^^^^^^^^

If you want to create a new xml document from scratch then please use the syntax:
    doc = REXML::Document.new

If you want to write it to something use an IO object...
    doc.write obj_to_output_to

where obj_to_output_to can be any object that responds to <<, so an IO object, a string, a StringIO, etc...

Zach