BabyErubis.rb

$Release: 2.0.0 $

BabyErubis is an yet another eRuby implementation, based on Erubis.

Small and fast
Easy to customize
Supports HTML as well as plain text
Accepts both template file and template string
Supports Ruby on Rails template

BabyErubis supports Ruby >= 1.8 and Rubinius >= 2.0.

Examples

Render template string:

require 'baby_erubis'
template = BabyErubis::Html.new.from_str <<'END', __FILE__, __LINE__+1
  <h1><%= @title %></h1>
  <% for item in @items %>
    <p><%= item %></p>
  <% end %>
END
context = {:title=>'Example', :items=>['A', 'B', 'C']}
output = template.render(context)
print output

Render template file:

require 'baby_erubis'
templat = BabyErubis::Html.new.from_file('example.html.erb', 'utf-8')
context = {:title=>'Example', :items=>['A', 'B', 'C']}
output = template.render(context)
print output

(Use BabyErubis::Text instead of BabyErubis::Html when rendering plain text.)

Command-line examples (see baby_erubis.rb --help for details):

## convert eRuby file into Ruby code
$ baby_erubis -x   file.erb     # text
$ baby_erubis -xH  file.erb     # html
$ baby_erubis -X   file.erb     # embedded code only
## render eRuby file with context data
$ baby_erubis -c '{items: [A, B, C]}'   file.erb    # YAML
$ baby_erubis -c '@items=["A","B","C"]' file.erb    # Ruby
$ baby_erubis -f data.yaml file.erb                 # or -f *.json, *.rb
## debug eRuby file
$ baby_erubis -xH file.erb | ruby -wc     # check syntax error
$ baby_erubis -XHNU file.erb              # show embedded ruby code

Template Syntax

<% ... %> : Ruby statement
<%= ... %> : Ruby expression with escaping
<%== ... %> : Ruby expression without escaping

Expression in <%= ... %> is escaped according to template class.

BabyErubis::Text doesn't escape anything. It justs converts expression into a string.
BabyErubis::Html escapes html special characters. It converts < > & " ' into < > & " ' respectively.

(Experimental) <%- ... -%> and <%-= ... -%> are handled same as <% ... %> and <%= ... %> respectively.

(Experimental) Block argument expression supported since version 2.0. Example:

## template
<%== form_for(:article) do |f| %>
  ...
<% end %>

## compiled ruby code
 _buf << form_for(:article) do |f| _buf << '
  ...
'; end;

Advanced Topics

Template Context

When rendering template, you can pass not only Hash object but also any object as context values. Internally, rendering method converts Hash object into BabyErubis::TemplateContext object automatically.

Example:

require 'baby_erubis'

class MyApp
  include BabyErubis::HtmlEscaper  # necessary to define escape()

  TEMPLATE = BabyErubis::Html.new.from_str <<-'END', __FILE__, __LINE__+1
    <html>
      <body>
        <p>Hello <%= @name %>!</p>
      </body>
    </html>
  END

  def initialize(name)
    @name = name
  end

  def render()
    return TEMPLATE.render(self)   # use self as context object
  end

end

if __FILE__ == $0
  print MyApp.new('World').render()
end

String#freeze()

BabyErubis supports String#freeze() automatically when on Ruby version >= 2.1. And you can control whether to use freeze() or not.

template_str = <<'END'
<div>
<b><%= message %></b>
</div>
END

## don't use freeze()
t = BabyErubis::Text.new(:freeze=>false).from_str(template_str)
print t.src
# --- result ---
# _buf = ''; _buf << '<div>
# <b>'; _buf << (message).to_s; _buf << '</b>
# </div>
# '; _buf.to_s

## use freeze() forcedly
t = BabyErubis::Text.new(:freeze=>true).from_str(template_str)
print t.src
# --- result ---
# _buf = ''; _buf << '<div>
# <b>'.freeze; _buf << (message).to_s; _buf << '</b>
# </div>
# '.freeze; _buf.to_s

Ruby on Rails Template

BabyErubis::RailsTemplate class generates Rails-style ruby code.

require 'baby_erubis'
require 'baby_erubis/rails'

t = BabyErubis::RailsTemplate.new.from_str <<'END'
<div>
  <%= form_for :article do |f| %>
    ...
  <% end %>
</div>
END
print t.src

Result:

@output_buffer = output_buffer || ActionView::OutputBuffer.new;@output_buffer.safe_append='<div>
  ';@output_buffer.append= form_for :article do |f| ;@output_buffer.safe_append='
    ...
'.freeze;   end;
@output_buffer.safe_append='</div>
';@output_buffer.to_s

You can check syntax of Rails template in command-line:

$ baby_erubis -Rx app/views/articles/index.html.erb | ruby -wc

(TODO: How to use BabyErubis in Ruby on Rails instead of Erubis)

Customizing

Change Embed Pattern from '<% %>' to '%'

Sample code:

require 'baby_erubis'

class MyTemplate < BabyErubis::Html

  rexp = BabyErubis::Template::PATTERN
  PATTERN = Regexp.compile(rexp.to_s.sub(/<%/, '\{%').sub(/%>/, '%\}'))

  def pattern
    PATTERN
  end

end

template = MyTemplate.new <<-'END'
{% for item in @items %}
- {%= item %}
{% end %}
END

print template.render(:items=>['A', 'B', 'C'])

Output:

- A
- B
- C

Strip Spaces in HTML Template

Sample code:

require 'baby_erubis'

class MyTemplate < BabyErubis::Html

  def parse(input, *args)
    stripped = input.gsub(/^[ \t]+</, '<')
    return super(stripped, *args)
  end

end

template = MyTemplate.new <<-'END'
  <html>
    <body>
      <p>Hello <%= @name %>!</p>
    </body>
  </html>
END

print template.render(:name=>"Hello")

Output:

<html>
<body>
<p>Hello Hello!</p>
</body>
</html>

Layout Template

Sample code:

require 'baby_erubis'

class MyApp
  include BabyErubis::HtmlEscaper  # necessary to define escape()

  LAYOUT = BabyErubis::Html.new.from_str <<-'END', __FILE__, __LINE__+1
    <html>
      <body>
        <% _buf << @_content %>    # or <%== @_content %>
      </body>
    </html>
  END

  TEMPLATE = BabyErubis::Html.new.from_str <<-'END', __FILE__, __LINE__+1
    <p>Hello <%= @name %>!</p>
  END

  def initialize(name)
    @name = name
  end

  def render()
    @_content = TEMPLATE.render(self)
    return LAYOUT.render(self)
  end

end

if __FILE__ == $0
  print MyApp.new('World').render()
end

Output:

  <html>
    <body>
          <p>Hello World!</p>
    </body>
  </html>

Template Cache File

Sample code:

require 'baby_erubis'
require 'logger'

$logger = Logger.new(STDERR)

class MyTemplate < BabyErubis::Html

  def from_file(filename, encoding='utf-8')
    cachefile = "#{filename}.cache"
    timestamp = File.mtime(filename)
    has_cache = File.file?(cachefile) && File.mtime(cachefile) == timestamp
    if has_cache
      $logger.info("loading template from cache file: #{cachefile}")
      ruby_code = File.open(cachefile, "rb:#{encoding}") {|f| f.read }
      compile(ruby_code, filename, 1)
    else
      super(filename, encoding)
      $logger.info("creating template cache file: #{cachefile}")
      ruby_code = self.src
      tmpname = "#{cachefile}.#{rand().to_s[2,5]}"
      File.open(tmpname, "wb:#{encoding}") {|f| f.write(ruby_code) }
      File.utime(timestamp, timestamp, tmpname)
      File.rename(tmpname, cachefile)
    end
    return self
  end

end

p File.exist?('example.html.erb.cache')   #=> false
t = MyTemplate.new.from_file('example.html.erb')
p File.exist?('example.html.erb.cache')   #=> true

Todo

[Done] Support Rails syntax (= <%= form_for do |f| %>)

Changes

Release 2.0.0 (2014-12-09)

[enhance] Ruby on Rails template support
[enhance] Block argument expression support
[enhance] New command-line option '-R' and '--format=rails'

Release 1.0.0 (2014-05-17)

[enhance] Provides script file bin/baby_erubis.
[enhance] Supports Ruby 1.8 and Rubinius 2.x.
[change] Define 'BabyErubis::RELEASE'.
[bugfix] 'Template#render()' creates context object when nil passed.

Release 0.1.0 (2014-05-06)

Public release

License

$License: MIT License $

BabyErubis.rb

Examples

Template Syntax

Advanced Topics

Template Context

String#freeze()

Ruby on Rails Template

Customizing

Change Embed Pattern from '<% %>' to '%'

Strip Spaces in HTML Template

Layout Template

Template Cache File

Todo

Changes

Release 2.0.0 (2014-12-09)

Release 1.0.0 (2014-05-17)

Release 0.1.0 (2014-05-06)

License

Copyright