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class Array
# 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.
#
# Array.wrap(nil) # => []
# Array.wrap([1, 2, 3]) # => [1, 2, 3]
# Array.wrap(0) # => [0]
#
# 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>Array.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.
#
# 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:
#
# [*object]
#
# which returns <tt>[nil]</tt> 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.
def self.wrap(object)
if object.nil?
[]
elsif object.respond_to?(:to_ary)
object.to_ary
else
[object]
end
end
end
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