BigDecimal 不能被强制转换为 BigDecimal答案

【问题标题】：BigDecimal can't be coerced into BigDecimalBigDecimal 不能被强制转换为 BigDecimal
【发布时间】：2012-05-30 06:08:18
【问题描述】：

这应该很简单，但它正在爆炸。有什么想法吗？

d = BigDecimal.new("2.0")
YAML::load({:a => d}.to_yaml)
TypeError: BigDecimal can't be coerced into BigDecimal
from /Users/benjohnson/.rvm/rubies/ruby-1.9.3-p125/lib/ruby/1.9.1/irb/inspector.rb:86:in `inspect'
from /Users/benjohnson/.rvm/rubies/ruby-1.9.3-p125/lib/ruby/1.9.1/irb/inspector.rb:86:in `inspect'
from /Users/benjohnson/.rvm/rubies/ruby-1.9.3-p125/lib/ruby/1.9.1/irb/inspector.rb:86:in `block in <module:IRB>'
from /Users/benjohnson/.rvm/rubies/ruby-1.9.3-p125/lib/ruby/1.9.1/irb/inspector.rb:30:in `call'
from /Users/benjohnson/.rvm/rubies/ruby-1.9.3-p125/lib/ruby/1.9.1/irb/inspector.rb:30:in `inspect_value'
from /Users/benjohnson/.rvm/rubies/ruby-1.9.3-p125/lib/ruby/1.9.1/irb/context.rb:260:in `inspect_last_value'
from /Users/benjohnson/.rvm/rubies/ruby-1.9.3-p125/lib/ruby/1.9.1/irb.rb:311:in `output_value'
from /Users/benjohnson/.rvm/rubies/ruby-1.9.3-p125/lib/ruby/1.9.1/irb.rb:160:in `block (2 levels) in eval_input'
from /Users/benjohnson/.rvm/rubies/ruby-1.9.3-p125/lib/ruby/1.9.1/irb.rb:273:in `signal_status'
from /Users/benjohnson/.rvm/rubies/ruby-1.9.3-p125/lib/ruby/1.9.1/irb.rb:156:in `block in eval_input'
from /Users/benjohnson/.rvm/rubies/ruby-1.9.3-p125/lib/ruby/1.9.1/irb/ruby-lex.rb:243:in `block (2 levels) in each_top_level_statement'
from /Users/benjohnson/.rvm/rubies/ruby-1.9.3-p125/lib/ruby/1.9.1/irb/ruby-lex.rb:229:in `loop'
from /Users/benjohnson/.rvm/rubies/ruby-1.9.3-p125/lib/ruby/1.9.1/irb/ruby-lex.rb:229:in `block in each_top_level_statement'
from /Users/benjohnson/.rvm/rubies/ruby-1.9.3-p125/lib/ruby/1.9.1/irb/ruby-lex.rb:228:in `catch'
from /Users/benjohnson/.rvm/rubies/ruby-1.9.3-p125/lib/ruby/1.9.1/irb/ruby-lex.rb:228:in `each_top_level_statement'
from /Users/benjohnson/.rvm/rubies/ruby-1.9.3-p125/lib/ruby/1.9.1/irb.rb:155:in `eval_input'
from /Users/benjohnson/.rvm/rubies/ruby-1.9.3-p125/lib/ruby/1.9.1/irb.rb:70:in `block in start'
from /Users/benjohnson/.rvm/rubies/ruby-1.9.3-p125/lib/ruby/1.9.1/irb.rb:69:in `catch'
from /Users/benjohnson/.rvm/rubies/ruby-1.9.3-p125/lib/ruby/1.9.1/irb.rb:69:in `start'
from /Users/benjohnson/.rvm/rubies/ruby-1.9.3-p125/bin/irb:16:in `<main>'Maybe IRB bug!

【问题讨论】：

嗯，看起来 to_yaml 对 BigDecimal 感到困惑，BigDecimal.new("2.0").to_yaml 表示 "--- !ruby/object:BigDecimal {}\n\n"。
是的。 ActiveSupport 似乎为此添加了核心扩展，但在我的平台上，我得到了 BigDecimal.new("2.0").to_yaml -> "--- 2.0\n"。所以虽然效果更好，但它仍然不能转换为完整的BigDecimal:apidock.com/rails/BigDecimal/to_yaml

标签： ruby serialization yaml bigdecimal

【解决方案1】：

这是reported 和fixed 一直存在的错误。

最好的解决方案是升级到最新的 Ruby（修复在补丁级别 194 以上）。

如果您无法升级您的 Ruby 版本，您可以通过安装 Psych gem 来获得修复。如果你这样做，你需要在require 'yaml' 之前添加gem 'psych'（或者如果你使用的是Bundler，则将它添加到你的Gemfile）以从gem而不是标准库中加载代码..

【讨论】：

【解决方案2】：

是的，我遇到过一次。这是我所做的一个版本：

YAML & BigDecimal workaround

【讨论】：

不幸的是，该解决方案不再有效。我在 ruby 1.9.3

【解决方案3】：

这是 David 的答案，感谢this related question，已更新到 1.9.3：

require 'yaml'
require 'bigdecimal'
YAML::ENGINE.yamler= 'syck'
class BigDecimal
  def to_yaml(opts={})
    YAML::quick_emit(object_id, opts) do |out|
      out.scalar("tag:induktiv.at,2007:BigDecimal", self.to_s)
    end
  end
end
YAML.add_domain_type("induktiv.at,2007", "BigDecimal") do |type, val|
  BigDecimal.new(val)
end
x = BigDecimal.new("2.0")
puts x.to_yaml
y = YAML.load(x.to_yaml)
puts x == y

【讨论】：