How to get categories of a post for an Octopress plugin in class Liquid::Tag -

i have code:

module jekyll   class connexetag < liquid::tag     def render(context)       categories = get_categories(context)       categories.class.name # => "array"       # categories # => "category1category2"       # categories.join(',') # => error !       # categories.size # => error !     end      private      def get_categories(context)       context.environments.first["page"]["categories"]     end   end end 

it outputs array, , that's ok. when try methods on categories, size or each error:

building site: source -> public liquid exception: undefined method `size' nil:nilclass in atom.xml /home/xavier/octopress/plugins/connexe_tag.rb:25:in `render' 

i can't apply methods on categories. tell me doing wrong here ?

happily, fix simple. problem code assumes every page have array of categories. isn't case atom.xml context.environments.first["page"]["categories"] return nil which, of course, doesn't have method 'size'. can set output if get_categories returns value , you're set.

module jekyll   class connexetag < liquid::tag     def render(context)       categories = get_categories(context)        # return list of categories pages have them       categories.join(', ') if categories     end      private      def get_categories(context)       context.environments.first["page"]["categories"]     end   end end   liquid::template.register_tag('connexe_tag', jekyll::connexetag) 

that should it.