Alternative to #to_a and Array(...)

Note: In Rails 3+ you can use Array.wrap Show archive.org snapshot instead of the solution here.

In the past you could use Array(...) or #to_a to turn an object into an array, unless it already is an array:

CopyArray(5) # => [5]
Array([5]) # => [5]

Unfortunately this idiom has issues and it also triggers deprecation warnings like this one:

Copywarning: default `to_a' will be obsolete

For an alternative you can copy the attached file to config/initializers or require it from a non-Rails project. You can now say:

Copy5.listify # => [5]
[5].listify # => [5]

Note that this method no longer treats nil receivers as a special case:

CopyArray(nil) # => []
nil.listify # => [nil]