Class: Lexorank::Ranking

Inherits:
Object
  • Object
show all
Includes:
Lexorank
Defined in:
lib/lexorank/ranking.rb

Constant Summary

Constants included from Lexorank

MAX_CHAR, MIN_CHAR, VERSION

Instance Attribute Summary collapse

Instance Method Summary collapse

Methods included from Lexorank

#get_char, #mid, #value_between

Constructor Details

#initialize(record_class:, field:, group_by:, advisory_lock:) ⇒ Ranking

Returns a new instance of Ranking.



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# File 'lib/lexorank/ranking.rb', line 8

def initialize(record_class:, field:, group_by:, advisory_lock:)
  @record_class = record_class
  @original_field = field
  @field = process_column_name(field)
  @original_group_by = group_by
  @group_by = process_group_by_column_name(group_by)
  @advisory_lock_config = { enabled: record_class.respond_to?(:with_advisory_lock) }.merge(advisory_lock)
end

Instance Attribute Details

#advisory_lock_config ⇒ Object (readonly)

Returns the value of attribute advisory_lock_config.



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# File 'lib/lexorank/ranking.rb', line 6

def advisory_lock_config
  @advisory_lock_config
end

#field ⇒ Object (readonly)

Returns the value of attribute field.



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# File 'lib/lexorank/ranking.rb', line 6

def field
  @field
end

#group_by ⇒ Object (readonly)

Returns the value of attribute group_by.



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# File 'lib/lexorank/ranking.rb', line 6

def group_by
  @group_by
end

#original_field ⇒ Object (readonly)

Returns the value of attribute original_field.



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# File 'lib/lexorank/ranking.rb', line 6

def original_field
  @original_field
end

#original_group_by ⇒ Object (readonly)

Returns the value of attribute original_group_by.



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# File 'lib/lexorank/ranking.rb', line 6

def original_group_by
  @original_group_by
end

#record_class ⇒ Object (readonly)

Returns the value of attribute record_class.



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# File 'lib/lexorank/ranking.rb', line 6

def record_class
  @record_class
end

Instance Method Details

#advisory_lock_name(instance) ⇒ Object 



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# File 'lib/lexorank/ranking.rb', line 95

def advisory_lock_name(instance)
  if advisory_lock_config[:lock_name].present?
    advisory_lock_config[:lock_name].(instance)
  else
    "#{record_class.table_name}_update_#{field}".tap do |name|
      if group_by.present?
        name << "_group_#{instance.send(group_by)}"
      end
    end
  end
end

#advisory_locks_enabled? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/lexorank/ranking.rb', line 107

def advisory_locks_enabled?
  record_class.respond_to?(:with_advisory_lock) && advisory_lock_config[:enabled]
end

#move_to(instance, position) ⇒ Object 



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# File 'lib/lexorank/ranking.rb', line 36

def move_to(instance, position)
  if block_given? && advisory_locks_enabled?
    return with_lock_if_enabled(instance) do
      move_to(instance, position)
      yield
    end
  end

  collection = record_class.ranked
  if group_by.present?
    collection = collection.where("#{group_by}": instance.send(group_by))
  end

  # exceptions:
  #   move to the beginning (aka move to position 0)
  #   move to end (aka position = collection.size - 1)
  # when moving to the end of the collection the offset and limit statement automatically handles
  # that 'after' is nil which is the same like [collection.last, nil]
  before, after =
    if position == :last
      [collection.last, nil]
    elsif position.zero?
      [nil, collection.first]
    else
      collection.where.not(id: instance.id).offset(position - 1).limit(2)
    end

  # If position >= collection.size both `before` and `after` will be nil. In this case
  # we set before to the last element of the collection
  if before.nil? && after.nil?
    before = collection.last
  end

  rank =
    if (self == after && send(field).present?) || (before == self && after.nil?)
      send(field)
    else
      value_between(before&.send(field), after&.send(field))
    end

  instance.send(:"#{field}=", rank)

  if block_given?
    yield
  else
    rank
  end
end

#validate! ⇒ Object 



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# File 'lib/lexorank/ranking.rb', line 17

def validate!
  if advisory_lock_config[:enabled] && !record_class.respond_to?(:with_advisory_lock)
    raise(
      Lexorank::InvalidConfigError,
      "Cannot enable advisory lock if #{record_class.name} does not respond to #with_advisory_lock. " \
      'Consider installing the with_advisory_lock gem (https://rubygems.org/gems/with_advisory_lock).'
    )
  end

  unless @field
    # TODO: Make this raise an error. Supplying an invalid column should raise.
    warn "The supplied ranking column \"#{@original_field}\" is not a column of the model!"
  end

  if original_group_by && !group_by
    warn "The supplied grouping by \"#{original_group_by}\" is neither a column nor an association of the model!"
  end
end

#with_lock_if_enabled(instance) ⇒ Object 



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# File 'lib/lexorank/ranking.rb', line 85

def with_lock_if_enabled(instance, &)
  if advisory_locks_enabled?
    advisory_lock_options = advisory_lock_config.except(:enabled, :lock_name)

    record_class.with_advisory_lock(advisory_lock_name(instance), **advisory_lock_options, &)
  else
    yield
  end
end