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module Arel
class Header
include Enumerable
def initialize(attrs = [])
@attributes = attrs.to_ary
@names = {}
end
def each
to_ary.each { |e| yield e }
self
end
def [](key)
case key
when String, Symbol then find_by_name(key)
when Attribute then find_by_attribute(key)
end
end
def ==(other)
to_set == other.to_set
end
def union(other)
new(to_ary | other)
end
alias | union
def to_ary
@attributes
end
def bind(relation)
Header.new(map { |a| a.bind(relation) })
end
# TMP
def index(i)
to_ary.index(i)
end
private
def new(attrs)
self.class.new(attrs)
end
def matching(attribute)
select { |a| !a.is_a?(Value) && a.root == attribute.root }
end
def find_by_name(name)
k = name.to_sym
@names[k] ||= @attributes.detect { |a| a.named?(k) }
end
def find_by_attribute(attr)
matching(attr).max do |a, b|
(a.original_attribute / attr) <=> (b.original_attribute / attr)
end
end
end
end
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