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module Arel
module Predicates
class Predicate
def or(other_predicate)
Or.new(self, other_predicate)
end
def |(other_predicate)
Or.new(self, other_predicate)
end
def and(other_predicate)
And.new(self, other_predicate)
end
def &(other_predicate)
And.new(self, other_predicate)
end
def complement
Not.new(self)
end
def not
complement
end
if respond_to?('!') # Nice! We're running Ruby 1.9 and can override the inherited BasicObject#!
def empty? # Need to define empty? to keep Object#blank? from going haywire
false
end
define_method('!') do
self.complement
end
end
end
class Polyadic < Predicate
attributes :predicates
def initialize(*predicates)
@predicates = predicates
end
# Build a Polyadic predicate based on:
# * <tt>operator</tt> - The Predicate subclass that defines the type of operation
# (LessThan, Equality, etc)
# * <tt>operand1</tt> - The left-hand operand (normally an Arel::Attribute)
# * <tt>additional_operands</tt> - All possible right-hand operands
def self.build(operator, operand1, *additional_operands)
new(
*additional_operands.uniq.inject([]) do |predicates, operand|
predicates << operator.new(operand1, operand)
end
)
end
def ==(other)
same_elements?(@predicates, other.predicates)
end
def bind(relation)
self.class.new(
*predicates.map {|p| p.find_correlate_in(relation)}
)
end
private
def same_elements?(a1, a2)
[:select, :inject, :size].each do |m|
return false unless [a1, a2].each {|a| a.respond_to?(m) }
end
a1.inject({}) { |h,e| h[e] = a1.select { |i| i == e }.size; h } ==
a2.inject({}) { |h,e| h[e] = a2.select { |i| i == e }.size; h }
end
end
class Any < Polyadic
def complement
All.new(*predicates.map {|p| p.complement})
end
end
class All < Polyadic
def complement
Any.new(*predicates.map {|p| p.complement})
end
end
class Unary < Predicate
attributes :operand
deriving :initialize, :==
def bind(relation)
self.class.new(operand.find_correlate_in(relation))
end
end
class Not < Unary
def complement
operand
end
end
class Binary < Predicate
attributes :operand1, :operand2
deriving :initialize
def ==(other)
self.class === other and
@operand1 == other.operand1 and
@operand2 == other.operand2
end
def bind(relation)
self.class.new(operand1.find_correlate_in(relation), operand2.find_correlate_in(relation))
end
end
class CompoundPredicate < Binary; end
class And < CompoundPredicate
def complement
Or.new(operand1.complement, operand2.complement)
end
end
class Or < CompoundPredicate
def complement
And.new(operand1.complement, operand2.complement)
end
end
class Equality < Binary
def ==(other)
Equality === other and
((operand1 == other.operand1 and operand2 == other.operand2) or
(operand1 == other.operand2 and operand2 == other.operand1))
end
def complement
Inequality.new(operand1, operand2)
end
end
class Inequality < Equality
def complement
Equality.new(operand1, operand2)
end
end
class GreaterThanOrEqualTo < Binary
def complement
LessThan.new(operand1, operand2)
end
end
class GreaterThan < Binary
def complement
LessThanOrEqualTo.new(operand1, operand2)
end
end
class LessThanOrEqualTo < Binary
def complement
GreaterThan.new(operand1, operand2)
end
end
class LessThan < Binary
def complement
GreaterThanOrEqualTo.new(operand1, operand2)
end
end
class Match < Binary
def complement
NotMatch.new(operand1, operand2)
end
end
class NotMatch < Binary
def complement
Match.new(operand1, operand2)
end
end
class In < Binary
def complement
NotIn.new(operand1, operand2)
end
end
class NotIn < Binary
def complement
In.new(operand1, operand2)
end
end
end
end
|
