Class: Tap::Tasks::Load

Inherits:
Tap::Task show all
Defined in:
lib/tap/tasks/load.rb

Overview

:startdoc::manifest the default load task

Load YAML-formatted data, as may be produced using Tap::Dump, and makes this data available for other tasks. Load is often used as a gateway task to other tasks.

% tap run -- load FILEPATH --: [task]

Load can select items from Hash or Array objects using one or more keys when only a subset is desired. By default items are selected using []. For more flexible selection, use match.

Match converts each of the keys to a Regexp. For hashes, all values with a matching key will be selected. For arrays, any item matching a regexp will be selected.

Use the flags to flatten, compact, sort (etc) results before passing them on to the next task.

Constant Summary

Constants inherited from Tap::Task

Tap::Task::DEFAULT_HELP_TEMPLATE

Instance Attribute Summary

Attributes inherited from Tap::Task

#name

Attributes included from Support::Executable

#app, #batch, #dependencies, #method_name, #on_complete_block

Instance Method Summary collapse

Methods inherited from Tap::Task

execute, help, inherited, #initialize, #initialize_batch_obj, #inspect, instance, intern, load, #log, parse, parse!, #to_s, use

Methods included from Support::Executable

#_execute, #batch_index, #batch_with, #batched?, #check_terminate, #depends_on, #enq, #execute, #fork, initialize, #initialize_batch_obj, #merge, #on_complete, #reset_dependencies, #resolve_dependencies, #sequence, #switch, #sync_merge, #unbatched_depends_on, #unbatched_enq, #unbatched_on_complete

Constructor Details

This class inherits a constructor from Tap::Task

Instance Method Details

#process(input, *keys) ⇒ Object

Loads the input as YAML and selects objects using keys. Input may be an IO, StringIO, or a filepath. If keys are empty, the loaded object is returned directly.

Key Selection

Keys select items from the loaded object using [] (ie obj). If match==true, the behavior is different; each string key is converted into a Regexp and then arrays select items that match key:

results = []
array.each {|i| results << i if i =~ key}

While hashes select values where the key matches key:

results = []
hash.each_pair {|k,v| results << v if k =~ key}

Other objects raise an error when match is true.

Post Processing

After loading/key selection, the results may be processed (in this order) using flatten, compact, unique, and sort, each performing as you would expect.



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# File 'lib/tap/tasks/load.rb', line 55

def process(input, *keys)
  
  # load the input
  obj = case input
  when StringIO, IO
    YAML.load(input.read)
  else
    log :load, input
    YAML.load_file(input)
  end
  
  # select results by key
  results = case
  when keys.empty? then obj
  when match 
    regexps = keys.collect {|key| Regexp.new(key.to_s) }
    select_matching(obj, regexps)
  else 
    keys.collect do |key| 
      index = key.kind_of?(String) ? YAML.load(key) : key
      obj[index]
    end
  end
  
  # post-process results
  results = results.flatten if flatten
  results = results.compact if compact
  results = results.uniq if unique
  results = results.sort if sort
  
  #if preview
    # should be a log or something
    #puts results.inspect
  #end
  
  results
end