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# Most objects are cloneable, but not all. For example you can't dup +nil+:
#
# nil.dup # => TypeError: can't dup NilClass
#
# Classes may signal their instances are not duplicable removing +dup+/+clone+
# or raising exceptions from them. So, to dup an arbitrary object you normally
# use an optimistic approach and are ready to catch an exception, say:
#
# arbitrary_object.dup rescue object
#
# Rails dups objects in a few critical spots where they are not that arbitrary.
# That rescue is very expensive (like 40 times slower than a predicate), and it
# is often triggered.
#
# That's why we hardcode the following cases and check duplicable? instead of
# using that rescue idiom.
class Object
# Can you safely .dup this object?
# False for nil, false, true, symbols, numbers, class and module objects; true otherwise.
def duplicable?
true
end
end
class NilClass
# Instances of NilClass are not duplicable
#
# === Example
#
# nil.duplicable? # => false
# nil.dup # => TypeError: can't dup NilClass
def duplicable?
false
end
end
class FalseClass
# Instances of FalseClass are not duplicable
#
# === Example
#
# false.duplicable? # => false
# false.dup # => TypeError: can't dup FalseClass
def duplicable?
false
end
end
class TrueClass
# Instances of TrueClass are not duplicable
#
# === Example
#
# true.duplicable? # => false
# true.dup # => TypeError: can't dup TrueClass
def duplicable?
false
end
end
class Symbol
# Symbols are not duplicable
#
# === Example
#
# :my_symbol.duplicable? # => false
# :my_symbol.dup # => TypeError: can't dup Symbol
def duplicable?
false
end
end
class Numeric #:nodoc:
def duplicable?
false
end
end
class Class #:nodoc:
def duplicable?
false
end
end
class Module #:nodoc:
def duplicable?
false
end
end
|
