diff options
Diffstat (limited to 'railties')
| -rw-r--r-- | railties/guides/source/active_support_core_extensions.textile | 29 |
1 files changed, 26 insertions, 3 deletions
diff --git a/railties/guides/source/active_support_core_extensions.textile b/railties/guides/source/active_support_core_extensions.textile index fcf4ae29ba..136fcde82a 100644 --- a/railties/guides/source/active_support_core_extensions.textile +++ b/railties/guides/source/active_support_core_extensions.textile @@ -2214,14 +2214,27 @@ NOTE: Defined in +active_support/core_ext/array/conversions.rb+. h4. Wrapping -The class method +Array.wrap+ behaves like the function +Array()+ except: +The method +Array.wrap+ wraps its argument in an array unless it is already an array (or array-like). + +Specifically: + +* If the argument is +nil+ an empty list is returned. +* Otherwise, if the argument responds to +to_ary+ it is invoked, and its result returned. +* Otherwise, returns an array with the argument as its single element. + +<ruby> +Array.wrap(nil) # => [] +Array.wrap([1, 2, 3]) # => [1, 2, 3] +Array.wrap(0) # => [0] +</ruby> + +This method is similar in purpose to <tt>Kernel#Array</tt>, but there are some differences: * If the argument responds to +to_ary+ the method is invoked. <tt>Kernel#Array</tt> moves on to try +to_a+ if the returned value is +nil+, but <tt>Arraw.wrap</tt> returns such a +nil+ right away. * If the returned value from +to_ary+ is neither +nil+ nor an +Array+ object, <tt>Kernel#Array</tt> raises an exception, while <tt>Array.wrap</tt> does not, it just returns the value. * It does not call +to_a+ on the argument, though special-cases +nil+ to return an empty array. - - that it does not try to call +to_a+ on its argument. That changes the behavior for enumerables: +The last point is particularly worth comparing for some enumerables: <ruby> Array.wrap(:foo => :bar) # => [{:foo => :bar}] @@ -2231,6 +2244,16 @@ Array.wrap("foo\nbar") # => ["foo\nbar"] Array("foo\nbar") # => ["foo\n", "bar"], in Ruby 1.8 </ruby> +There's also a related idiom that uses the splat operator: + +<ruby> +[*object] +</ruby> + +which returns +[nil]+ for +nil+, and calls to <tt>Array(object)</tt> otherwise + +Thus, in this case the behavior is different for +nil+, and the differences with <tt>Kernel#Array</tt> explained above apply to the rest of +object+s. + NOTE: Defined in +active_support/core_ext/array/wrap.rb+. h4. Grouping |