Question

I’m trying out Builder::XMLMarkup to build some xml and it keeps adding an empty element to my xml.

Why does it do this and how do I stop it?

xml = Builder::XmlMarkup.new
=> <inspect/> 

Answer 1

Builder implements a version of method_missing that adds tags given by the name of the method call.

Assuming you are playing in irb (or rails’ console), irb’s default behaviour when you evaluate an expression (such as Builder::XmlMarkup.new) is to call inspect on it, in order to generate a string to show to you. In the case of builder, inspect isn’t the usual ruby inspect method – it falls through to method_missing and adds the tag.

This will only happen when playing with ruby interactively. You can do stuff like

xml = Builder::XmlMarkup.new; false

Here the result of the expression is false so irb calls inspect on that and leaves your builder object alone.

It can be awkward to keep doing this continually. If you do

xml = Builder::XmlMarkup.new; false
def xml.inspect; target!; end

then xml will still be a builder object that display its content when inspected by irb. You won’t be able to create tags called inspect (other than by using tag!) but that is usually a minor inconvenience.