Add Hash#transform_keys and Hash#transform_keys! and refactor *_keys methods to use them.
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## Rails 4.0.0 (unreleased) ##
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* Add `Hash#transform_keys` and `Hash#transform_keys!`. *Mark McSpadden*
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* Changed xml type `datetime` to `dateTime` (with upper case letter `T`). *Angelo Capilleri*
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* Add `:instance_accessor` option for `class_attribute`. *Alexey Vakhov*
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@ -1,23 +1,37 @@
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class Hash
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# Return a new hash with all keys converted using the block operation.
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#
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# { :name => 'Rob', :years => '28' }.transform_keys{ |key| key.to_s.upcase }
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# # => { "NAME" => "Rob", "YEARS" => "28" }
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def transform_keys
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result = {}
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keys.each do |key|
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result[yield(key)] = self[key]
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end
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result
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end
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# Destructively convert all keys using the block operations.
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# Same as transform_keys but modifies +self+
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def transform_keys!
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keys.each do |key|
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self[yield(key)] = delete(key)
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end
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self
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end
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# Return a new hash with all keys converted to strings.
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#
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# { :name => 'Rob', :years => '28' }.stringify_keys
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# #=> { "name" => "Rob", "years" => "28" }
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def stringify_keys
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result = {}
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keys.each do |key|
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result[key.to_s] = self[key]
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end
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result
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transform_keys{ |key| key.to_s }
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end
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# Destructively convert all keys to strings. Same as
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# +stringify_keys+, but modifies +self+.
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def stringify_keys!
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keys.each do |key|
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self[key.to_s] = delete(key)
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end
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self
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transform_keys!{ |key| key.to_s }
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end
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# Return a new hash with all keys converted to symbols, as long as
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@ -26,21 +40,14 @@ class Hash
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# { 'name' => 'Rob', 'years' => '28' }.symbolize_keys
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# #=> { :name => "Rob", :years => "28" }
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def symbolize_keys
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result = {}
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keys.each do |key|
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result[(key.to_sym rescue key)] = self[key]
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end
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result
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transform_keys{ |key| key.to_sym rescue key }
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end
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alias_method :to_options, :symbolize_keys
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# Destructively convert all keys to symbols, as long as they respond
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# to +to_sym+. Same as +symbolize_keys+, but modifies +self+.
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def symbolize_keys!
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keys.each do |key|
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self[(key.to_sym rescue key)] = delete(key)
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end
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self
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transform_keys!{ |key| key.to_sym rescue key }
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end
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alias_method :to_options!, :symbolize_keys!
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@ -28,10 +28,13 @@ class HashExtTest < ActiveSupport::TestCase
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@mixed = { :a => 1, 'b' => 2 }
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@fixnums = { 0 => 1, 1 => 2 }
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@illegal_symbols = { [] => 3 }
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@upcase_strings = { 'A' => 1, 'B' => 2 }
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end
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def test_methods
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h = {}
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assert_respond_to h, :transform_keys
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assert_respond_to h, :transform_keys!
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assert_respond_to h, :symbolize_keys
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assert_respond_to h, :symbolize_keys!
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assert_respond_to h, :stringify_keys
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@ -40,6 +43,18 @@ class HashExtTest < ActiveSupport::TestCase
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assert_respond_to h, :to_options!
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end
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def test_transform_keys
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assert_equal @upcase_strings, @strings.transform_keys{ |key| key.to_s.upcase }
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assert_equal @upcase_strings, @symbols.transform_keys{ |key| key.to_s.upcase }
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assert_equal @upcase_strings, @mixed.transform_keys{ |key| key.to_s.upcase }
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end
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def test_transform_keys!
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assert_equal @upcase_strings, @symbols.dup.transform_keys!{ |key| key.to_s.upcase }
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assert_equal @upcase_strings, @strings.dup.transform_keys!{ |key| key.to_s.upcase }
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assert_equal @upcase_strings, @mixed.dup.transform_keys!{ |key| key.to_s.upcase }
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end
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def test_symbolize_keys
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assert_equal @symbols, @symbols.symbolize_keys
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assert_equal @symbols, @strings.symbolize_keys
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@ -2549,6 +2549,38 @@ There's also the bang variant +except!+ that removes keys in the very receiver.
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NOTE: Defined in +active_support/core_ext/hash/except.rb+.
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h5. +transform_keys+ and +transform_keys!+
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The method +transform_keys+ accepts a block and returns a hash that has applied the block operations to each of the keys in the receiver:
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<ruby>
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{nil => nil, 1 => 1, :a => :a}.transform_keys{ |key| key.to_s.upcase }
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# => {"" => nil, "A" => :a, "1" => 1}
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</ruby>
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The result in case of collision is undefined:
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<ruby>
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{"a" => 1, :a => 2}.transform_keys{ |key| key.to_s.upcase }
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# => {"A" => 2}, in my test, can't rely on this result though
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</ruby>
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This method may be useful for example to build specialized conversions. For instance +stringify_keys+ and +symbolize_keys+ use +transform_keys+ to perform their key conversions:
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<ruby>
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def stringify_keys
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transform_keys{ |key| key.to_s }
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end
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...
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def symbolize_keys
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transform_keys{ |key| key.to_sym rescue key }
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end
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</ruby>
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There's also the bang variant +transform_keys!+ that applies the block operations to keys in the very receiver.
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NOTE: Defined in +active_support/core_ext/hash/keys.rb+.
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h5. +stringify_keys+ and +stringify_keys!+
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The method +stringify_keys+ returns a hash that has a stringified version of the keys in the receiver. It does so by sending +to_s+ to them:
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