How to test the value of ensure in a custom type?

I've been writing custom types for Puppet, and I've run into a case where for both 'latest' and 'present' I require the existence of certain parameters, but for 'absent' I would like those parameters to be optional.

Unfortunately, I haven't been able to figure out how to test the value of 'ensure' within the ruby code.

Puppet::Type.type(:fubar) do
  ensurable do
    desc 'Has three states: absent, present, and latest.'
    newvalue(:absent) do
      # ...
    end

    newvalue(:latest) do
      # ...
    end

    newvalue(:present) do
      # ...
    end

    def insync?(is)
      # ...
    end

    defaultto :latest
  end

  # ...

  validate do
    # This if condition doesn't work.  The error is still raised.
    if :ensure != :absent
      unless value(:myprop)
        raise ArgumentError, "Property 'myprop' is required."
      end
    end
  end
end

So, my question is simple... How do I test the value of 'ensure' so that when it is 'absent', the validation is NOT performed?

Solution

Thanks to both Matt Schuchard and John Bollinger for their help.

The problem is that:

if :ensure != :absent

is indeed comparing two symbols, where I need to be comparing the value of a property to a symbol:

if self[:ensure] != :absent

I am sufficiently new to both Puppet and Ruby that I didn't realize the difference. John stated it clearly, and Matt provided a good example.

Again, Thanks to both Matt and John.