View helper, blocks and capture. Template output is repeated (rails 3)

rubyonrails-talk
1

I'm having some issues with blocks and capture in erb templates, and the particular problem shows itself in that the expected output in the template view is repeated due to something related to how capture works. (Using Rails 3.x)

I have the following view helper:

module ColumnLayoutHelper

  def layout_columns(options = {}, &content_block)     raise ArgumentError, "No block given" unless block_given?

    layout = ColumnLayoutBuilder.new     layout.configure(options)     content = capture(layout, &content_block)     content_tag(:div, content, layout.main_wrapping, false)

  end

end

class ColumnLayoutBuilder < Object

  include ActionView::Helpers::TagHelper   include ActionView::Helpers::CaptureHelper

  attr_accessor :output_buffer, :column_counter   attr_accessor :main_wrapping   attr_accessor :column_wrapping

  def configure(options)     @main_wrapping = options.delete(:main_wrapping)     @column_wrapping = options.delete(:column_wrapping)   end

  def column(&block)

    raise ArgumentError, "No block given" unless block_given?

    @column_counter ||= 0     @column_counter = @column_counter + 1

    column_html_options = (column_wrapping ? column_wrapping.dup : {})

{}

    column_html_options.default = ""     column_html_options[:class] = "column_#{column_counter} " + column_html_options[:class]     column_content = content_tag(:div, capture(self, &block), column_html_options,false)     column_content   end

end

2

I'm having some issues with blocks and capture in erb templates, and the particular problem shows itself in that the expected output in the template view is repeated due to something related to how capture works. (Using Rails 3.x)

Here's my hunch: capture swaps in a temporary output buffer to capture the output. However because you've got your custom builder object, the call to capture inside your builder object is fiddling with the builder's output buffer attribute, which is neither here nor there because the bits of erb you yield to know nothing of this arrangement an d are writing to the template's output_buffer

If you look at the source for fields_for/Formbuilder you can see that they squirrel away the template object (in your helper method this is just self) for later. You should probably do the same

Fred