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class Hash
# Slices a hash to include only the given keys. Returns a hash containing
# the given keys.
#
# { a: 1, b: 2, c: 3, d: 4 }.slice(:a, :b)
# # => {:a=>1, :b=>2}
#
# This is useful for limiting an options hash to valid keys before
# passing to a method:
#
# def search(criteria = {})
# criteria.assert_valid_keys(:mass, :velocity, :time)
# end
#
# search(options.slice(:mass, :velocity, :time))
#
# If you have an array of keys you want to limit to, you should splat them:
#
# valid_keys = [:mass, :velocity, :time]
# search(options.slice(*valid_keys))
def slice(*keys)
keys.map! { |key| convert_key(key) } if respond_to?(:convert_key, true)
keys.each_with_object(self.class.new) { |k, hash| hash[k] = self[k] if has_key?(k) }
end
# Replaces the hash with only the given keys.
# Returns a hash containing the removed key/value pairs.
#
# { a: 1, b: 2, c: 3, d: 4 }.slice!(:a, :b)
# # => {:c=>3, :d=>4}
def slice!(*keys)
keys.map! { |key| convert_key(key) } if respond_to?(:convert_key, true)
omit = slice(*self.keys - keys)
hash = slice(*keys)
hash.default = default
hash.default_proc = default_proc if default_proc
replace(hash)
omit
end
# Removes and returns the key/value pairs matching the given keys.
#
# { a: 1, b: 2, c: 3, d: 4 }.extract!(:a, :b) # => {:a=>1, :b=>2}
# { a: 1, b: 2 }.extract!(:a, :x) # => {:a=>1}
def extract!(*keys)
keys.each_with_object(self.class.new) { |key, result| result[key] = delete(key) if has_key?(key) }
end
end
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