wrap(object) public

Wraps its argument in an array unless it is already an array (or array-like).


  • 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.

    Array.wrap(nil) # => [] Array.wrap([1, 2, 3]) # => [1, 2, 3] Array.wrap(0) # => [0]

This method is similar in purpose to Kernel#Array, but there are some differences:

  • If the argument responds to to_ary the method is invoked. Kernel#Array

moves on to try to_a if the returned value is nil, but Array.wrap returns such a nil right away.

  • If the returned value from to_ary is neither nil nor an Array object, Kernel#Array

raises an exception, while Array.wrap 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.

The last point is particularly worth comparing for some enumerables:

Array(:foo => :bar)      # => [[:foo, :bar]]
Array.wrap(:foo => :bar) # => [{:foo => :bar}]

Array("foo\nbar")        # => ["foo\n", "bar"], in Ruby 1.8
Array.wrap("foo\nbar")   # => ["foo\nbar"]

There’s also a related idiom that uses the splat operator:


which returns [nil] for nil, and calls to Array(object) otherwise.

Thus, in this case the behavior is different for nil, and the differences with Kernel#Array explained above apply to the rest of +object+s.

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