如何在 Ruby 中解冻对象

发布于02月26日

在Ruby中，有Object#freeze个选项，可以防止进一步修改对象:

class Kingdom
  attr_accessor :weather_conditions
end

arendelle = Kingdom.new
arendelle.frozen? # => false
arendelle.weather_conditions = 'in deep, deep, deep, deep snow'
arendelle.freeze
arendelle.frozen? # => true
arendelle.weather_conditions = 'sun is shining'
  # !> RuntimeError: can't modify frozen Kingdom

script = 'Do you want to build a snowman?'.freeze
script[/snowman/] = 'castle of ice'
  # !> RuntimeError: can't modify frozen String

然而，没有Object#unfreeze个.有没有办法解冻一个冰冻的王国？

推荐答案

不，根据documentation for Object#freeze:

没有办法解冻冻结的物体.

冻结状态存储在对象中.调用freeze设置冻结状态，从而防止进一步修改.这包括修改对象的冻结状态.

关于您的示例，您可以指定一个新字符串:

script = 'Do you want to build a snowman?'
script.freeze

script = script.dup if script.frozen?
script[/snowman/] = 'castle of ice'
script #=> "Do you want to build a castle of ice?"

Ruby 2.3引入了String#+@，因此可以编写+str而不是str.dup if str.frozen?