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Contents
# frozen_string_literal: true
#--
# Most objects are cloneable, but not all. For example you can't dup methods:
#
# method(:puts).dup # => TypeError: allocator undefined for Method
#
# 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 method objects;
# true otherwise.
def duplicable?
true
end
end
methods_are_duplicable = begin
Object.instance_method(:duplicable?).dup
true
rescue TypeError
false
end
unless methods_are_duplicable
class Method
# Methods are not duplicable:
#
# method(:puts).duplicable? # => false
# method(:puts).dup # => TypeError: allocator undefined for Method
def duplicable?
false
end
end
class UnboundMethod
# Unbound methods are not duplicable:
#
# method(:puts).unbind.duplicable? # => false
# method(:puts).unbind.dup # => TypeError: allocator undefined for UnboundMethod
def duplicable?
false
end
end
end
require "singleton"
module Singleton
# Singleton instances are not duplicable:
#
# Class.new.include(Singleton).instance.dup # TypeError (can't dup instance of singleton
def duplicable?
false
end
end
Version data entries
34 entries across 34 versions & 4 rubygems