BigDecimal无法转换为BigDecimal

Question

这应该很简单，但却出了问题。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!

- Binary Logic

---

嗯，看起来 to_yaml 在处理 BigDecimal 时有些混乱，BigDecimal.new("2.0").to_yaml 的输出是 "--- !ruby/object:BigDecimal {}\n\n"。 - mu is too short

是的。ActiveSupport 似乎为此添加了一个核心扩展，但在我的平台上，我得到 BigDecimal.new("2.0").to_yaml -> "--- 2.0\n"。所以虽然它工作得更好，但仍无法转换为完整的 BigDecimal：http://apidock.com/rails/BigDecimal/to_yaml - Casper

Answer 1

这是一个已经报告并修复的错误。

最好的解决方案是升级到最新的Ruby版本（修复程序从补丁级别194开始）。

如果您无法升级Ruby版本，可以通过安装Psych gem来获取修复程序。 如果这样做，您需要在require 'yaml'之前添加gem 'psych'（或者如果您正在使用Bundler，则将其添加到您的Gemfile中），以从gem加载代码而不是从标准库中加载。

- matt

Answer 2

这是David的答案，经过更新以适用于1.9.3，感谢这个相关问题：

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

- rampion

Answer 3

是的，我曾经遇到过这个问题。这是我所做的版本：

YAML & BigDecimal 解决方法

- David

---

不幸的是，那个解决方案已经不再适用了。我使用的是 Ruby 1.9.3。 - Binary Logic