stp-che · February 29, 2016 11:28
diff --git a/gistfile1.rb b/gistfile1.rb
 require 'active_support/all'

 class A < HashWithIndifferentAccess
 end

 class B < HashWithIndifferentAccess
  def initialize(*args)
    super
    freeze
  end
 end

 a = A.new.tap &:freeze
 p a.merge(x: 1)    # => {"x"=>1}

 b = B.new
 p b.merge(x: 1)    # .../active_support/hash_with_indifferent_access.rb:125:in `default=': can't modify frozen B (RuntimeError)
	require 'active_support/all'

	class A < HashWithIndifferentAccess
	end

	class B < HashWithIndifferentAccess
	def initialize(*args)
	super
	freeze
	end
	end

	a = A.new.tap &:freeze
	p a.merge(x: 1) # => {"x"=>1}

	b = B.new
	p b.merge(x: 1) # .../active_support/hash_with_indifferent_access.rb:125:in `default=': can't modify frozen B (RuntimeError)