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class Module
# Automatically generate sorting definitions based on attribute fields.
#
# sort_on :a, :b
#
# _is equivalent to_
#
# def <=>(o)
# cmp = self.a <=> o.a; return cmp unless cmp == 0
# cmp = self.b <=> o.b; return cmp unless cmp == 0
# 0
# end
#
# TO BE DEPRECATED
def compare_on(*fields)
code = %{def <=>(o)\n}
fields.each { |f|
code << %{cmp = ( @#{f} <=> o.instance_variable_get('@#{f}') );
return cmp unless cmp == 0\n}
}
code << %{0\nend; alias_method :cmp, :<=>;}
class_eval( code )
fields
end
# Should this be a standard alias?
alias_method :sort_on, :compare_on
# Deprecated usage
#alias_method :sort_attributes, :sort_on
end
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