explains Array.wrap directly, rather by comparison with Kernel#Array which is too obscure, leaves the comparison to document the differences, and adds a comparison with the related idiom that uses the splat operator

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