Output haml content via :ruby filter

问题

When I use the :ruby filter to do some simple stuff in haml, for example...

:ruby
  to = comments > max_comments ? max_comments : comments
  (0...to).each do |i|
    comment = data[i]
    puts li_comment comment[0], comment[1], comment[2]
  end

the puts statement writes the output to the console. The docs for :ruby indicate that it

Creates an IO object named haml_io, anything written to it is output into the Haml document.

How exactly does one use the haml_io object to write to the haml document, but not to the console (think I need something other than puts)?

回答1:

This behaviour changed recently – the old behaviour (before version 4.0) was to write anything written to standard out to the Haml document, but this wasn’t thread safe.

haml_io is a local variable that refers to an IO object that writes to the document. Your code rewritten to use it would look something like this (assuming comments, max_comments and li_comment are all defined earlier):

:ruby
  to = comments > max_comments ? max_comments : comments
  (0...to).each do |i|
    comment = data[i]
    haml_io.puts li_comment comment[0], comment[1], comment[2]
  end

haml_io is actually a StringIO object so you can use any of its methods, e.g. haml_io.write, haml_io.putc and it will redirect output to your document.

回答2:

... Call puts on haml_io?

Anything written to it is output into the Haml document.

回答3:

Note that if you are using https://github.com/k0kubun/hamlit as your renderer rather than plain https://github.com/haml/haml, the syntax for this is different again. It appears you just need to return the value you want from the filter.

None of the standard haml API's appear to work:

[46] pry(main)> Hamlit::Template.new() { ":ruby\n  puts 'aaa'" }.render
aaa
=> ""

[47] pry(main)> Hamlit::Template.new() { ":ruby\n  haml_io.puts 'aaa'" }.render
NameError: undefined local variable or method `haml_io' for #<Object:0x00007f9ec2f178a0>
from (__TEMPLATE__):1:in `__tilt_70159905806200'

[49] pry(main)> Hamlit::Template.new() { ":ruby\n  'aaa'" }.render
=> ""

But if you return from the :ruby filter, you get the output:

[50] pry(main)> Hamlit::Template.new() { ":ruby\n  return 'aaa'" }.render
=> "aaa"

I opened an issue about this, for reference: https://github.com/k0kubun/hamlit/issues/152

来源：https://stackoverflow.com/questions/17328758/output-haml-content-via-ruby-filter

标签

ruby

haml

middleman