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module Hashery
# StaticHash ia a Hash object which raises an error if any
# previously-defined key attempts to be set again.
#
# foo = StaticHash.new
# foo['name'] = 'Tom' #=> 'Tom'
# foo['age'] = 30 #=> 30
# foo['name'] = 'Bob'
#
# produces
#
# ArgumentError: Duplicate key for StaticHash -- 'name'
#
# StaticHash has it's orgins in Gavin Kistner's WriteOnceHash
# class found in his +basiclibrary.rb+ script.
#
# TODO: Maybe StaticHash isn't bets name for this class?
#
class StaticHash < CRUDHash
#
# Set a value for a key. Raises an error if that key already
# exists with a different value.
#
# key - Index key to associate with value.
# value - Value to associate with key.
#
# Retruns value.
#
def store(key, value)
if key?(key) && fetch(key) != value
raise ArgumentError, "Duplicate key for StaticHash -- #{key.inspect}"
end
super(key, value)
end
#
#def update(hash)
# dups = (keys | hash.keys)
# if dups.empty?
# super(hash)
# else
# raise ArgumentError, "Duplicate key for StaticHash -- #{dups.inspect}"
# end
#end
#
#alias_method :merge!, :update
end
end
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