Class: Compony::NaturalOrdering

Inherits:
Array
  • Object
show all
Defined in:
lib/compony/natural_ordering.rb

Overview

This class provides an array-based data structure where elements have symbol names. New elements can be appended or placed at a location using before:. Important: do not mutate this class with any other method call than the natural_-prefixed methods defined below. Example:

collection = Compony::NaturalOrdering.new
collection.natural_push(:a, a_payload)
collection.natural_push(:c, c_payload)
collection.natural_push(:b, b_payload, before: :c)
collection.natural_push(:d, d_payload, hidden: true)
collection.natural_push(:a, a_new_payload) # overwrites :a

collection.reject{|el| el.hidden}.map(&:name) # --> :a, :b, :c
collection.map(&:payload) # --> a_new_payload, b_payload, c_payload, d_payload

Instance Method Summary collapse

Instance Method Details

#natural_push(name, payload, before: nil, **kwargs) ⇒ Object 



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# File 'lib/compony/natural_ordering.rb', line 18

def natural_push(name, payload, before: nil, **kwargs)
  name = name.to_sym
  before_name = before&.to_sym
  old_kwargs = {}

  # Fetch existing element if any
  existing_index = find_index { |el| el.name == name }
  if existing_index.present?
    # Copy all non-mentionned kwargs from the element we are about to overwrite
    old_kwargs = self[existing_index].except(:name, :payload)

    # Replacing an existing element with a before: directive - must delete before calculating indices
    if before_name.present?
      delete_at(existing_index)
    end
  end

  # Fetch before element
  if before_name.present?
    before_index = find_index { |el| el.name == before_name } || fail("Element #{before_name.inspect} for :before not found in #{inspect}.")
  end

  # Create the element to insert
  element = MethodAccessibleHash.new(name:, payload:, **old_kwargs.merge(kwargs))

  # Insert new element
  if before_index.present?
    # Insert before another element
    insert(before_index, element)
  elsif existing_index.present?
    # Override another element
    self[existing_index] = element
  else
    # Append at the end
    self << element
  end
end