Class: Axiom::Relation::Operation::Sorted::Direction

Inherits:

Object

• Object
• Axiom::Relation::Operation::Sorted::Direction

Extended by:

Aliasable

Includes:

AbstractType

Defined in:

lib/axiom/relation/operation/sorted/direction.rb

Overview

Abstract base class for attribute sorting

Direct Known Subclasses

Ascending, Descending

Instance Attribute Summary

• #attribute ⇒ Attribute readonly private

  The attribute to sort on.

Class Method Summary

• .coerce(object) ⇒ Direction private

  Coerce an object into a Direction.

Instance Method Summary

• #call(left, right) ⇒ -1, ...

  Compare the left and right Tuple attribute values.

• #initialize(attribute) ⇒ undefined constructor private

  Initialize a Direction.

• #name ⇒ Symbol

  Return the attribute name.

• #rename(aliases) ⇒ self, Direction

  Rename the contained attribute with the provided aliases.

• #reverse ⇒ Direction

  Return the reverse Direction.

Methods included from Aliasable

inheritable_alias

Constructor Details

#initialize(attribute) ⇒ undefined

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future.

Initialize a Direction

Parameters:

• attribute (Attribute) —

  the attribute to sort on

# File 'lib/axiom/relation/operation/sorted/direction.rb', line 31

def initialize(attribute)
  @attribute = attribute
end

Instance Attribute Details

#attribute ⇒ Attribute (readonly)

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future.

The attribute to sort on

Returns:

• (Attribute)

# File 'lib/axiom/relation/operation/sorted/direction.rb', line 21

def attribute
  @attribute
end

Class Method Details

.coerce(object) ⇒ Direction

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future.

Coerce an object into a Direction

Parameters:

• object (Attribute, Direction) —

  the object to coerce

Returns:

• (Direction)

# File 'lib/axiom/relation/operation/sorted/direction.rb', line 108

def self.coerce(object)
  object.kind_of?(Direction) ? object : new(Attribute.coerce(object))
end

Instance Method Details

#call(left, right) ⇒ -1, ...

Compare the left and right Tuple attribute values

Examples:

comparison = direction.call(left, right)

Parameters:

• left (Tuple)
• right (Tuple)

Returns:

• (-1) —

  returned if the left should be sorted before the right

• (0) —

  returned if the left and right are equal

• (1) —

  returned if the left should be sorted after the right

# File 'lib/axiom/relation/operation/sorted/direction.rb', line 65

def call(left, right)
  self.class.call(attribute.call(left), attribute.call(right))
end

#name ⇒ Symbol

Return the attribute name

Examples:

direction.name  # => :id

Returns:

• (Symbol)

# File 'lib/axiom/relation/operation/sorted/direction.rb', line 43

def name
  attribute.name
end

#rename(aliases) ⇒ self, Direction

Rename the contained attribute with the provided aliases

Examples:

renamed = direction.rename(aliases)

Parameters:

• aliases (Algebra::Rename::Aliases) —

  the old and new attributes

Returns:

• (self) —

  if the attribute is not renamed

• (Direction) —

  if the attribute is renamed

# File 'lib/axiom/relation/operation/sorted/direction.rb', line 83

def rename(aliases)
  renamed = aliases[attribute]
  renamed.equal?(attribute) ? self : self.class.new(renamed)
end

#reverse ⇒ Direction

Return the reverse Direction

Examples:

reversed = direction.reverse

Returns:

• (Direction)

# File 'lib/axiom/relation/operation/sorted/direction.rb', line 96

def reverse
  self.class.reverse.new(attribute)
end