blocks|key|3197967|text|我认为为了在你的项目中拥有有凝聚力的源文件，你应该在类中定义错误，在这个类中可能抛出它们，而不是在其他地方。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3197968|一些层级结构可能是有帮助的-名称空间擅长于将多余的字符串排除在类型名称之外-但这更多的是一个品味问题-如果你的应用程序中至少有一个自定义异常类型，你可以在整个过程中使用它来区分“有意的”和“意外的”异常情况，那么就没有必要走得太远。|3197969|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|F|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|G|8|@]|9|@]|A|$]]|$1|D|3|-4|5|6|7|H|8|@]|9|@]|A|$]]]|E|$]]

I think in order to have cohesive source files in your project, you should define errors in the class in which may throw them and nowhere else.

Some heirarchy can be helpful - namespaces are good at keeping redundant strings out of type names - but that's more a matter of taste - there's no need to go overboard provided you have at least one custom exception type in your app which you use throughout to differentiate between 'intentional' and 'accidental' exception cases.

blocks|key|2984735|text|针对Gems的|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2984736|我见过很多次，你是这样定义异常的：|offset|length|style|BOLD|2984737|2984738|+gem目录/库/gem名称/Exceptions.rb|blockquote|2984739|2984740|2984741|并定义为：|2984742|module+GemName

++class+AuthenticationError+<+StandardError;+end
++class+InvalidUsername+<+AuthenticationError;+end

end|code-block|syntax|javascript|2984743|在httparty中就是这样的例子|2984744|Ruby+on+Rails的|2984745|将它们放在库/文件夹中的一个名为exceptions.rb的文件下，如下所示：|2984746|module+Exceptions
++class+AuthenticationError+<+StandardError;+end
++class+InvalidUsername+<+AuthenticationError;+end
end|2984747|你可以这样使用它：|2984748|raise+Exceptions::InvalidUsername|2984749|entityMap|0|LINK|mutability|MUTABLE|url|https://github.com/jnunemaker/httparty/blob/master/lib/httparty/exceptions.rb^0|0|0|H|0|0|0|S|0|0|0|0|5|0|0|0|H|1|8|0|0|0|D|0|0|13|0|0|0|9|0|0^^$0|@$1|2|3|4|5|6|7|1E|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|1F|8|@$D|1G|E|1H|F|G]]|9|@]|A|$]]|$1|H|3|-4|5|6|7|1I|8|@]|9|@]|A|$]]|$1|I|3|J|5|K|7|1J|8|@$D|1K|E|1L|F|G]]|9|@]|A|$]]|$1|L|3|-4|5|6|7|1M|8|@]|9|@]|A|$]]|$1|M|3|-4|5|6|7|1N|8|@]|9|@]|A|$]]|$1|N|3|O|5|6|7|1O|8|@$D|1P|E|1Q|F|G]]|9|@]|A|$]]|$1|P|3|Q|5|R|7|1R|8|@]|9|@]|A|$S|T]]|$1|U|3|V|5|6|7|1S|8|@$D|1T|E|1U|F|G]]|9|@$D|1V|E|1W|1|1X]]|A|$]]|$1|W|3|X|5|6|7|1Y|8|@$D|1Z|E|20|F|G]]|9|@]|A|$]]|$1|Y|3|Z|5|6|7|21|8|@$D|22|E|23|F|G]]|9|@]|A|$]]|$1|10|3|11|5|R|7|24|8|@]|9|@]|A|$S|T]]|$1|12|3|13|5|6|7|25|8|@$D|26|E|27|F|G]]|9|@]|A|$]]|$1|14|3|15|5|R|7|28|8|@]|9|@]|A|$S|T]]|$1|16|3|-4|5|6|7|29|8|@]|9|@]|A|$]]]|17|$18|$5|19|1A|1B|A|$1C|1D]]]]

For Gems

I have seen many times that you define exceptions in this way:

<blockquote>
 gem_dir/lib/gem_name/exceptions.rb
</blockquote>

and defined as:

<pre><code>module GemName

 class AuthenticationError &lt; StandardError; end
 class InvalidUsername &lt; AuthenticationError; end

end
</code></pre>

an example of this would be something like this in <a href="https://github.com/jnunemaker/httparty/blob/master/lib/httparty/exceptions.rb">httparty</a>

For Ruby on Rails

Put them in your lib/ folder under a file called exceptions.rb, which would look something like this:

<pre><code>module Exceptions
 class AuthenticationError &lt; StandardError; end
 class InvalidUsername &lt; AuthenticationError; end
end
</code></pre>

and you would use it like this:

<pre><code>raise Exceptions::InvalidUsername
</code></pre>

blocks|key|2984755|text|为了确保在Rails+4.1.10中为多个自定义错误类执行自动加载，您需要为每个类指定单独的文件。这应该可以在动态重新加载的开发中工作。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2984756|这是我在最近的一个项目中设置错误的方法：|2984757|在lib/app_name/error/base.rb中|offset|length|style|CODE|2984758|module+AppName
++++module+Error
++++++++class+Base+<+StandardError;+end
++++end
end|code-block|syntax|javascript|2984759|在随后的自定义错误中，如在lib/app_name/error/bad_stuff.rb中|2984760|module+AppName
++++module+Error
++++++++class+BadStuff+<+::AppName::Error::Base;+end
++++end
end|2984761|然后，您应该能够通过以下方式调用错误：|2984762|+raise+AppName::Error::BadStuff.new("Bad+stuff+just+happened")|2984763|entityMap^0|0|0|1|Q|0|0|D|V|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Y|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|Z|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|10|8|@$F|11|G|12|H|I]]|9|@]|A|$]]|$1|J|3|K|5|L|7|13|8|@]|9|@]|A|$M|N]]|$1|O|3|P|5|6|7|14|8|@$F|15|G|16|H|I]]|9|@]|A|$]]|$1|Q|3|R|5|L|7|17|8|@]|9|@]|A|$M|N]]|$1|S|3|T|5|6|7|18|8|@]|9|@]|A|$]]|$1|U|3|V|5|L|7|19|8|@]|9|@]|A|$M|N]]|$1|W|3|-4|5|6|7|1A|8|@]|9|@]|A|$]]]|X|$]]

To ensure that autoloading works as expected in Rails 4.1.10 for multiple custom error classes, you'll want to specify separate files for each. This should work in development with its dynamically reloading. 

This is how I setup errors in a recent project:

In <code>lib/app_name/error/base.rb</code>

<pre><code>module AppName
 module Error
 class Base &lt; StandardError; end
 end
end
</code></pre>

and in subsequent custom errors, like in <code>lib/app_name/error/bad_stuff.rb</code>

<pre><code>module AppName
 module Error
 class BadStuff &lt; ::AppName::Error::Base; end
 end
end
</code></pre>

You should then be able to call your errors via:

<pre><code> raise AppName::Error::BadStuff.new("Bad stuff just happened")
</code></pre>

blocks|key|3198046|text|在rails中，您可以创建app/errors目录|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|3198047|#+app/errors/foo_error.rb
class+FooError+<+StandardError;+end|code-block|syntax|javascript|3198048|重新启动spring/server，它应该会重新启动它|3198049|entityMap^0|D|A|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@$9|P|A|Q|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|R|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|S|8|@]|D|@]|E|$]]|$1|M|3|-4|5|6|7|T|8|@]|D|@]|E|$]]]|N|$]]

in rails you can make <code>app/errors</code> directory

<pre><code># app/errors/foo_error.rb
class FooError &lt; StandardError; end
</code></pre>

restart spring/server and it should pick it up

blocks|key|3198084|text|这是一个古老的问题，但我想分享我是如何在Rails中处理自定义错误的，包括附加错误消息、测试以及如何使用ActiveRecord模型处理此问题。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|3198085|创建自定义错误|3198086|class+MyClass
++#+create+a+custome+error
++class+MissingRequirement+<+StandardError;+end

++def+my_instance_method
++++raise+MyClass::MissingRequirement,+"My+error+msg"+unless+true+++
++end
end|code-block|syntax|javascript|3198087|测试(最小)|3198088|test+"should+raise+MissingRequirement+if+____+is+missing"
++#+should+raise+an+error
++error+=+assert_raises(MyClass::MissingRequirement)+{
++++MyClass.new.my_instance_method
++}

++assert+error.message+=+"My+error+msg"
end|3198089|使用ActiveRecord|3198090|我认为值得注意的是，如果使用ActiveRecord模型，一个流行的模式是向模型添加一个错误，如下所述，这样您的验证将失败：|3198091|def+MyModel+<+ActiveRecord::Base
++validate+:code_does_not_contain_hyphens

++def+code_does_not_contain_hyphens
++++errors.add(:code,+"cannot+contain+hyphens")+if+code.include?("-")
++end
end|3198092|当验证运行时，此方法将利用ActiveRecord的ActiveRecord::RecordInvalid错误类，并将导致验证失败。|3198093|希望这能有所帮助！|3198094|entityMap^0|1G|C|0|0|0|0|0|0|E|C|0|0|Q|R|0|0^^$0|@$1|2|3|4|5|6|7|12|8|@$9|13|A|14|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|15|8|@]|D|@]|E|$]]|$1|H|3|I|5|J|7|16|8|@]|D|@]|E|$K|L]]|$1|M|3|N|5|6|7|17|8|@]|D|@]|E|$]]|$1|O|3|P|5|J|7|18|8|@]|D|@]|E|$K|L]]|$1|Q|3|R|5|6|7|19|8|@]|D|@]|E|$]]|$1|S|3|T|5|6|7|1A|8|@$9|1B|A|1C|B|C]]|D|@]|E|$]]|$1|U|3|V|5|J|7|1D|8|@]|D|@]|E|$K|L]]|$1|W|3|X|5|6|7|1E|8|@$9|1F|A|1G|B|C]]|D|@]|E|$]]|$1|Y|3|Z|5|6|7|1H|8|@]|D|@]|E|$]]|$1|10|3|-4|5|6|7|1I|8|@]|D|@]|E|$]]]|11|$]]

This is an old question, but I wanted to share how I'm handling custom errors in Rails, including attaching error messages, testing, and how to handle this with <code>ActiveRecord</code> models. 

<h3>Creating Custom Error</h3>

<pre><code>class MyClass
 # create a custome error
 class MissingRequirement &lt; StandardError; end

 def my_instance_method
 raise MyClass::MissingRequirement, "My error msg" unless true 
 end
end
</code></pre>

<h3>Testing (minitest)</h3>

<pre><code>test "should raise MissingRequirement if ____ is missing"
 # should raise an error
 error = assert_raises(MyClass::MissingRequirement) {
 MyClass.new.my_instance_method
 }

 assert error.message = "My error msg"
end
</code></pre>

<h3>With ActiveRecord</h3>

I think it's worth noting that if working with an <code>ActiveRecord</code> model, a popular pattern is to add an error to the model as described below, so that your validations will fail:

<pre><code>def MyModel &lt; ActiveRecord::Base
 validate :code_does_not_contain_hyphens

 def code_does_not_contain_hyphens
 errors.add(:code, "cannot contain hyphens") if code.include?("-")
 end
end
</code></pre>

When validations are run, this method will piggy-back onto ActiveRecord's <code>ActiveRecord::RecordInvalid</code> error class and will cause validations to fail.

Hope this helps!

Is there a best practice for defining custom error types in a Ruby library (gem) or Ruby on Rails application? Specifically:

<ol>
<li>Where do they belong structurally in the project? A separate file, inlined with the relevant module/class definition, somewhere else?</li>
<li>Are there any conventions that establish when to and when not to create a new error type?</li>
</ol>

Different libraries have different ways of doing things, and I haven't noticed any real patterns. Some libraries always use custom error types while others don't use them at all; some have all errors extending StandardError while others have nested hierarchies; some are just empty class definitions, others have all sorts of clever tricks.

Oh, and just because I feel like calling these "error types" is sort of ambiguous, what I mean is this: 

<pre><code>class AuthenticationError &lt; StandardError; end
class InvalidUsername &lt; AuthenticationError; end
</code></pre>

Where to define custom error types in Ruby and/or Rails?

是否有在Ruby库(gem)或Ruby on Rails应用程序中定义自定义错误类型的最佳实践？具体地说：，它们在项目的结构上属于哪里？一个单独的文件，内联了相关的模块/类定义，在其他地方？是否有任何约定来确定何时以及何时不创建新的错误类型？不同的库有不同的处理方式，我没有注意到任何真正的模式。一些库总是使用自定义错误...

问在哪里定义Ruby和/或Rails中的自定义错误类型？
EN

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