Blockenspiel

Blockenspiel is a helper library designed to make it easy to implement DSL blocks. It is designed to be comprehensive and robust, supporting most common usage patterns, and working correctly in the presence of nested blocks and multithreading.

Summary

Blockenspiel is a helper library providing several different strategies for implementing DSL blocks. It supports both DSLs that take a block parameter and those that do not. For example:

 # Call DSL block with parameter
 configure_me do |config|
   config.add_foo(1)
   config.add_bar(2)
 end

 # Call DSL block without parameter
 configure_me do
   add_foo(3)
   add_bar(4)
 end

To support the above usage, you can do this:

 # Implement DSL block methods
 class ConfigMethods
   include Blockenspiel::DSL
   def add_foo(value)
     # do something
   end
   def add_bar(value)
     # do something
   end
 end

 # Implement configure_me method
 def configure_me(&block)
   Blockenspiel.invoke(block, ConfigMethods.new)
 end

By default, Blockenspiel uses a mixin technique (proposed by the late Why The Lucky Stiff) to support parameterless blocks without the complications introduced by instance_eval. It supports nested blocks and multithreaded access, and provides a variety of tools for handling the typical issues you may encounter when writing DSLs.

For more detailed usage and examples, see Blockenspiel.rdoc.

For an extended analysis of different ways to implement DSL blocks, see ImplementingDSLblocks.rdoc.

Requirements

• Ruby 1.8.6 or later (1.8.7 recommended), Ruby 1.9.1 or later, or JRuby 1.2 or later (1.4 recommended).

Installation

 gem install blockenspiel

Known issues and limitations

• Implementing wildcard DSL methods using method_missing doesn’t work. I haven’t yet figured out the right semantics for this case.
• Including Blockenspiel::DSL in a module is not yet supported, but this is planned in a future release.

Development and support

Documentation is available at virtuoso.rubyforge.org/blockenspiel/README_rdoc.html

Source code is hosted on Github at github.com/dazuma/blockenspiel

Report bugs on Github issues at github.org/dazuma/blockenspiel/issues

Contact the author at dazuma at gmail dot com.

Author / Credits

Blockenspiel is written by Daniel Azuma (www.daniel-azuma.com/).

The mixin implementation is based on a concept by the late Why The Lucky Stiff, documented in his 6 October 2008 blog posting entitled "Mixing Our Way Out Of Instance Eval?". The original link is gone, but you may find copies or mirrors out there.

The unmixer code is based on Mixology, version 0.1 by Patrick Farley, anonymous z, Dan Manges, and Clint Bishop. The code has been stripped down and modified to support MRI 1.9 and JRuby 1.2. I know Mixology 0.2 is available, but I’m keeping the unmixer bundled with Blockenspiel for now, to reduce dependencies.

License

Copyright 2008-2009 Daniel Azuma.

All rights reserved.

Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:

• Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.
• Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.
• Neither the name of the copyright holder, nor the names of any other contributors to this software, may be used to endorse or promote products derived from this software without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.