Command Designer

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Build command text based on multiple filters


This is framework to build command strings based on current context.

DSL Methods

  • initialize(priorities_array) - sets up initial context, execute all methods on this instance, try priorities: [:first, nil, :last]
  • filter(priority, options) { code } - create priority based filter for given options with the code bloc to execute
  • context(options) { code } - build new context, options are for matching filters, all code will be executes in context of given options
  • local_filter(filter_block) { code } - define local filter_block to take effect for the given code block, it's tricky as it takes two lambdas, try: local_filter({|cmd| "cd path && #{cmd}"}) { code }
  • command(name, *args) - build command by evaluate global and local filters in the order of given priority, local filters are called after the nil priority or on the end


subject =[:first, nil, :last])

subject.filter(:last,  {:server => "::2" }) {|cmd| "command #{cmd}" }
subject.filter(:first, {:target => "true"}) {|cmd| "env #{cmd}" }

subject.local_filter({|cmd| "cd /path && #{cmd}" }) do

  subject.command("true")  # => "cd /path && env true"
  subject.command("false") # => "cd /path && false"


subject.context(:server => "::2") do |server2|

  # the :last filter with "command" was applied on the end
  server2.command("true") # => "command env false"
  # you do not have to use the block variable, subject works fine too
  subject.command("false") # => "command false"