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class Hash
# Allows for reverse merging two hashes where the keys in the calling hash take precedence over those
# in the <tt>other_hash</tt>. This is particularly useful for initializing an option hash with default values:
#
# def setup(options = {})
# options.reverse_merge! :size => 25, :velocity => 10
# end
#
# The default <tt>:size</tt> and <tt>:velocity</tt> are only set if the +options+ hash passed in doesn't already
# have the respective key.
#
# As contrast, using Ruby's built in <tt>merge</tt> would require writing the following:
#
# def setup(options = {})
# options = { :size => 25, :velocity => 10 }.merge(options)
# end
def reverse_merge(other_hash)
other_hash.merge(self)
end
# Performs the opposite of <tt>merge</tt>, with the keys and values from the first hash taking precedence over the second.
# Modifies the receiver in place.
def reverse_merge!(other_hash)
# right wins if there is no left
merge!( other_hash ){|key,left,right| left }
end
alias_method :reverse_update, :reverse_merge!
end
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