capture

capture.rb

require 'erb'

class ERB
  class ERBOut
    Buffer = String # SafeBuffer if rails

    def initialize(s='')
      @str = Buffer.new(s)
    end
    
    def to_s
      @str
    end

    def <<(other)
      @str << other
    end

    def +(other)
      @str << other.to_s
      self
    end

    def capture(*arg, &block)
      save = @str
      @str = Buffer.new
      yield(*arg)
      return @str
    ensure
      @str = save
    end
  end

  def set_eoutvar(compiler, eoutvar = '_erbout')
    compiler.put_cmd = "#{eoutvar} << "
    compiler.insert_cmd = "#{eoutvar} += " # magic!!
    compiler.pre_cmd = ["#{eoutvar} = ERB::ERBOut.new"]
    compiler.post_cmd = ["#{eoutvar}.to_s"]
  end

  class Compiler
    def add_insert_cmd(out, content)
      out.push("#{@insert_cmd} #{content} ")
    end
  end
end

if __FILE__ == $0
  def capture(*arg, &block)
    block.binding.local_variable_get(:_erbout).capture(*arg, &block)
  end

  def form(*arg, &block)
    "<form>" + capture(*arg, &block).upcase + "</form>"
  end

  include ERB::Util

  src =<<RHTML
<%= form 'x' do |it| %>
<foo>
<%=h it %>
</foo>
<%= Time.now %>
<%=h 1.0%>
<%= 3.0 + 0.14 %>
<% end %>
RHTML

  erb = ERB.new(src)
  # puts erb.src
  result = erb.result(binding)
  puts result
end

% ruby capture.rb

X 2023-08-27 12:30:02 +0900 1.0 3.14