Filter Chain

Filter Chain is a Ruby gem for processing data through a chain of filters in an object oriented style.

Add this line to your application's Gemfile:

gem "filter_chain"

And then execute:

$ bundle

Or install it yourself as:

$ gem install filter_chain

A Chain is a container for a set of filters.

The below example serializes each input object to a JSON string, compresses the strings, prints the byte size of each string, and collects the results for future retrieval:

chain = FilterChain::Chain.new { |c|
  c.add(FilterChain::SerializeFilter.new(:format => :json))

  c.add(FilterChain::DeflateFilter.new)

  c.add(FilterChain::ProcFilter.new { |data|
    puts "Byte size: #{data.bytesize}"
    data
  })

  c.add(FilterChain::Collector.new)
}

chain << "Hello world"
chain << "How are you?"

puts chain.output.inspect

A Filter is an object that takes an input and passes it's output to the next link in a chain of filters. A number of filters are pre-defined:

• DeflateFilter
• InflateFilter
• SerializeFilter
• DeserializeFilter
• MultiplexFilter
• DemultiplexFilter
• ProcFilter
• Collector
• Terminator

You can easily create your own filters by inheriting from the Filter class and overriding the following handlers:

• on_initialize
• on_input(data)

You pass data to the next filter by calling the pass method in your on_input method.

A Collector is a specialized filter designed to be the last link in a chain. An array based collector is included, but you can easily define custom collectors using other data structures.

A Terminator takes the place of a collector when you want your last link to run a block of code.

Bug reports and pull requests are welcome on GitHub at https://github.com/chadrem/filter_chain.

The gem is available as open source under the terms of the MIT License.