Erbse

An updated version of Erubis.

Erbse compiles an ERB string to a string of Ruby.

API

The API is one public method.

Erbse::Engine.new.call("<% ... %>") #=> string of compiled ruby.

The returned string can then be evaluated in a certain context.

Output Buffers

Erbse does not use instance variables as output buffer, only local variables.

Tag	Behavior
<% %>	Executes the code but does not output anything.
<% .. do %>	Executes the code but does not output anything. In the block, output is written to the current buffer.
<%= %>	Executes the code, outputs to current buffer.
<%= .. do %>	Executes the code and appends returned value to the current buffer. In the block, output is written to a new buffer that is returned when yielding.
<%@ .. do %>	Executes the code but does not output anything. In the block, output is written to a new buffer that is returned when yielding.

Block Yielding

Erbse supports blocks à la Rails.

You may pass any mix of text/ERB via blocks to Ruby methods.

<%= form do %>
  <em>Please fill out all fields!</em>
  <%= input :email %>
  <button type="submit">
<% end %>

Here, the form method receives a block of compiled Ruby.

When yielded, the block simply returns its evaluated content as a string. It's your job to assign it to an output buffer, no instance variables are used.

def form(&block)
  content = yield
  "<form>#{content}</form>"
end

Usually, returning the content from the helper will be sufficient.

However, you can totally pass that block to a completely different object and yield it there. Since there's no global state as in ERB, this will work.

Capture

With the <%= helper do %> tag, block content is assigned to a new output buffer and the result of helper rendered.

To capture the block without outputting anything, use the <%@ %> tag. This will still use a new output buffer for the block, but not output anything.

<%@ content = capture do %>
  Whatever
<% end %>

<%= content %>

The capture method will receive a block, what you do with it is up to you. It would usually simply yield the block.

def capture(&block)
  yield
end

Removed Features

Erbse does not support any tags other than <% %>, <%= %> and <%@ %>. Tags such as <%% %>, <%== %>, <%- %> or <% -%> will be reduced to the supported tags.

TODO

The parser code got drastically reduced and might be missing essential features. Please report compiled syntax errors.

• Block comments
• Add newlines in compiled Ruby.

Planned

Block inheritance.

<h1><%= title %></h1>

<% fragment :subheader do %>
  Or: <%= subheader %>
<% end %>

This fragment could then be overridden.

Feel free to contribute!!!

Users

Erbse is the ERB engine in Cells.

License

MIT License

Contributors

• Special thanks to Aman Gupta for performance tweaks that are merged in Erbse.
• @iazel
• @seuros

Authors

• Copyright 2015 Nick Sutterer apotonick@gmail.com
• Copyright 2006-2011 makoto kuwata <kwa(at)kuwata-lab.com>