diff options
Diffstat (limited to 'guides/source/active_support_core_extensions.md')
| -rw-r--r-- | guides/source/active_support_core_extensions.md | 73 |
1 files changed, 11 insertions, 62 deletions
diff --git a/guides/source/active_support_core_extensions.md b/guides/source/active_support_core_extensions.md index 6c980fb0e9..73b24b900a 100644 --- a/guides/source/active_support_core_extensions.md +++ b/guides/source/active_support_core_extensions.md @@ -135,16 +135,14 @@ NOTE: Defined in `active_support/core_ext/object/blank.rb`. ### `duplicable?` -In Ruby 2.4 most objects can be duplicated via `dup` or `clone` except -methods and certain numbers. Though Ruby 2.2 and 2.3 can't duplicate `nil`, -`false`, `true`, and symbols as well as instances `Float`, `Fixnum`, -and `Bignum` instances. +As of Ruby 2.5, most objects can be duplicated via `dup` or `clone`: ```ruby "foo".dup # => "foo" "".dup # => "" -1.method(:+).dup # => TypeError: allocator undefined for Method -Complex(0).dup # => TypeError: can't copy Complex +Rational(1).dup # => (1/1) +Complex(0).dup # => (0+0i) +1.method(:+).dup # => TypeError (allocator undefined for Method) ``` Active Support provides `duplicable?` to query an object about this: @@ -152,35 +150,18 @@ Active Support provides `duplicable?` to query an object about this: ```ruby "foo".duplicable? # => true "".duplicable? # => true -Rational(1).duplicable? # => false -Complex(1).duplicable? # => false +Rational(1).duplicable? # => true +Complex(1).duplicable? # => true 1.method(:+).duplicable? # => false ``` -`duplicable?` matches Ruby's `dup` according to the Ruby version. - -So in 2.4: +`duplicable?` matches the current Ruby version's `dup` behavior, +so results will vary according the version of Ruby you're using. +In Ruby 2.4, for example, Complex and Rational are not duplicable: ```ruby -nil.dup # => nil -:my_symbol.dup # => :my_symbol -1.dup # => 1 - -nil.duplicable? # => true -:my_symbol.duplicable? # => true -1.duplicable? # => true -``` - -Whereas in 2.2 and 2.3: - -```ruby -nil.dup # => TypeError: can't dup NilClass -:my_symbol.dup # => TypeError: can't dup Symbol -1.dup # => TypeError: can't dup Fixnum - -nil.duplicable? # => false -:my_symbol.duplicable? # => false -1.duplicable? # => false +Rational(1).duplicable? # => false +Complex(1).duplicable? # => false ``` WARNING: Any class can disallow duplication by removing `dup` and `clone` or raising exceptions from them. Thus only `rescue` can tell whether a given arbitrary object is duplicable. `duplicable?` depends on the hard-coded list above, but it is much faster than `rescue`. Use it only if you know the hard-coded list is enough in your use case. @@ -2776,20 +2757,6 @@ Active Record does not accept unknown options when building associations, for ex NOTE: Defined in `active_support/core_ext/hash/keys.rb`. -### Working with Values - -#### `transform_values` && `transform_values!` - -The method `transform_values` accepts a block and returns a hash that has applied the block operations to each of the values in the receiver. - -```ruby -{ nil => nil, 1 => 1, :x => :a }.transform_values { |value| value.to_s.upcase } -# => {nil=>"", 1=>"1", :x=>"A"} -``` -There's also the bang variant `transform_values!` that applies the block operations to values in the very receiver. - -NOTE: Defined in `active_support/core_ext/hash/transform_values.rb`. - ### Slicing Ruby has built-in support for taking slices out of strings and arrays. Active Support extends slicing to hashes: @@ -2890,24 +2857,6 @@ end NOTE: Defined in `active_support/core_ext/regexp.rb`. -### `match?` - -Rails implements `Regexp#match?` for Ruby versions prior to 2.4: - -```ruby -/oo/.match?('foo') # => true -/oo/.match?('bar') # => false -/oo/.match?('foo', 1) # => true -``` - -The backport has the same interface and lack of side-effects in the caller like -not setting `$1` and friends, but it does not have the speed benefits. Its -purpose is to be able to write 2.4 compatible code. Rails itself uses this -predicate internally for example. - -Active Support defines `Regexp#match?` only if not present, so code running -under 2.4 or later does run the original one and gets the performance boost. - Extensions to `Range` --------------------- |