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module ActiveRelation
class Attribute
attr_reader :relation, :name, :alias
def initialize(relation, name, aliaz = nil)
@relation, @name, @alias = relation, name, aliaz
end
module Transformations
def as(aliaz = nil)
Attribute.new(relation, name, aliaz)
end
def substitute(new_relation)
Attribute.new(new_relation, name, @alias)
end
def qualify
self.as(qualified_name)
end
def to_attribute
self
end
end
include Transformations
def qualified_name
"#{relation.name}.#{name}"
end
def ==(other)
self.class == other.class and relation == other.relation and name == other.name and @alias == other.alias
end
module Predications
def equals(other)
Equality.new(self, other)
end
def less_than(other)
LessThan.new(self, other)
end
def less_than_or_equal_to(other)
LessThanOrEqualTo.new(self, other)
end
def greater_than(other)
GreaterThan.new(self, other)
end
def greater_than_or_equal_to(other)
GreaterThanOrEqualTo.new(self, other)
end
def matches(regexp)
Match.new(self, regexp)
end
end
include Predications
module Expressions
def count
Expression.new(self, "COUNT")
end
def sum
Expression.new(self, "SUM")
end
def maximum
Expression.new(self, "MAX")
end
def minimum
Expression.new(self, "MIN")
end
def average
Expression.new(self, "AVG")
end
end
include Expressions
def to_sql(strategy = Sql::Predicate.new)
strategy.attribute relation.name, name, self.alias
end
end
end
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