diff options
Diffstat (limited to 'guides/source/active_support_core_extensions.textile')
| -rw-r--r-- | guides/source/active_support_core_extensions.textile | 53 |
1 files changed, 53 insertions, 0 deletions
diff --git a/guides/source/active_support_core_extensions.textile b/guides/source/active_support_core_extensions.textile index 80faffa49c..587f65529e 100644 --- a/guides/source/active_support_core_extensions.textile +++ b/guides/source/active_support_core_extensions.textile @@ -2549,6 +2549,45 @@ There's also the bang variant +except!+ that removes keys in the very receiver. NOTE: Defined in +active_support/core_ext/hash/except.rb+. +h5. +transform_keys+ and +transform_keys!+ + +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: + +<ruby> +{nil => nil, 1 => 1, :a => :a}.transform_keys{ |key| key.to_s.upcase } +# => {"" => nil, "A" => :a, "1" => 1} +</ruby> + +The result in case of collision is undefined: + +<ruby> +{"a" => 1, :a => 2}.transform_keys{ |key| key.to_s.upcase } +# => {"A" => 2}, in my test, can't rely on this result though +</ruby> + +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: + +<ruby> +def stringify_keys + transform_keys{ |key| key.to_s } +end +... +def symbolize_keys + transform_keys{ |key| key.to_sym rescue key } +end +</ruby> + +There's also the bang variant +transform_keys!+ that applies the block operations to keys in the very receiver. + +Besides that, one can use +deep_transform_keys+ and +deep_transform_keys!+ to perform the block operation on all the keys in the given hash and all the hashes nested into it. An example of the result is: + +<ruby> +{nil => nil, 1 => 1, :nested => {:a => 3, 5 => 5}}.deep_transform_keys{ |key| key.to_s.upcase } +# => {""=>nil, "1"=>1, "NESTED"=>{"A"=>3, "5"=>5}} +</ruby> + +NOTE: Defined in +active_support/core_ext/hash/keys.rb+. + h5. +stringify_keys+ and +stringify_keys!+ 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: @@ -2579,6 +2618,13 @@ The second line can safely access the "type" key, and let the user to pass eithe There's also the bang variant +stringify_keys!+ that stringifies keys in the very receiver. +Besides that, one can use +deep_stringify_keys+ and +deep_stringify_keys!+ to stringify all the keys in the given hash and all the hashes nested into it. An example of the result is: + +<ruby> +{nil => nil, 1 => 1, :nested => {:a => 3, 5 => 5}}.deep_stringify_keys +# => {""=>nil, "1"=>1, "nested"=>{"a"=>3, "5"=>5}} +</ruby> + NOTE: Defined in +active_support/core_ext/hash/keys.rb+. h5. +symbolize_keys+ and +symbolize_keys!+ @@ -2613,6 +2659,13 @@ The second line can safely access the +:params+ key, and let the user to pass ei There's also the bang variant +symbolize_keys!+ that symbolizes keys in the very receiver. +Besides that, one can use +deep_symbolize_keys+ and +deep_symbolize_keys!+ to symbolize all the keys in the given hash and all the hashes nested into it. An example of the result is: + +<ruby> +{nil => nil, 1 => 1, "nested" => {"a" => 3, 5 => 5}}.deep_symbolize_keys +# => {nil=>nil, 1=>1, :nested=>{:a=>3, 5=>5}} +</ruby> + NOTE: Defined in +active_support/core_ext/hash/keys.rb+. h5. +to_options+ and +to_options!+ |