Ruby自定义错误类:消息属性的继承
Ruby自定义错误类:消息属性的继承
提问于 2013-04-19 22:11:14
我似乎找不到太多关于自定义异常类的信息。
我所知道的
您可以声明您的自定义error类，并让它从StandardError继承，因此它可以是rescued：
class MyCustomError < StandardError
end这使您可以使用以下命令来引发它：
raise MyCustomError, "A message"然后，在解救的时候得到这个信息
rescue MyCustomError => e
puts e.message # => "A message"我不知道什么
我想给我的异常提供一些自定义字段，但我想从父类继承message属性。我在读on this topic时发现@message不是exception类的实例变量，所以我担心我的继承无法工作。
有人能给我更多的细节吗？如何实现具有object属性的自定义error类？以下内容是否正确：
class MyCustomError < StandardError
attr_reader :object
def initialize(message, object)
super(message)
@object = object
end
end然后：
raise MyCustomError.new(anObject), "A message"要获得以下信息：
rescue MyCustomError => e
puts e.message # => "A message"
puts e.object # => anObject它会起作用吗?如果起作用，这是正确的做事方式吗？
回答 4
Stack Overflow用户
回答已采纳
发布于 2013-04-19 23:31:10
raise已经设置了消息，所以您不必将其传递给构造函数：
class MyCustomError < StandardError
attr_reader :object
def initialize(object)
@object = object
end
end
begin
raise MyCustomError.new("an object"), "a message"
rescue MyCustomError => e
puts e.message # => "a message"
puts e.object # => "an object"
end我已经用rescue MyCustomError替换了rescue Exception，参见Why is it a bad style to rescue Exception => e in Ruby?。
Stack Overflow用户
发布于 2016-08-20 18:02:08
鉴于所有其他错误都继承自Exception的ruby核心文档对#message的描述
返回调用exception.to_s的结果。通常会返回异常的消息或名称。通过提供to_str方法，异常同意在需要字符串的地方使用。
我会选择重新定义to_s/to_str或初始化器。下面是一个示例，我们希望以一种人类可读的方式知道外部服务何时做不到某件事。
注意:下面的第二个策略使用了rails的字符串方法，比如demodualize，这可能有点复杂，因此在异常中这样做可能是不明智的。如果需要，您还可以向方法签名添加更多参数。
覆盖#to_s策略而不是#to_str，它的工作方式不同
module ExternalService
class FailedCRUDError < ::StandardError
def to_s
'failed to crud with external service'
end
end
class FailedToCreateError < FailedCRUDError; end
class FailedToReadError < FailedCRUDError; end
class FailedToUpdateError < FailedCRUDError; end
class FailedToDeleteError < FailedCRUDError; end
end控制台输出
begin; raise ExternalService::FailedToCreateError; rescue => e; e.message; end
# => "failed to crud with external service"
begin; raise ExternalService::FailedToCreateError, 'custom message'; rescue => e; e.message; end
# => "failed to crud with external service"
begin; raise ExternalService::FailedToCreateError.new('custom message'); rescue => e; e.message; end
# => "failed to crud with external service"
raise ExternalService::FailedToCreateError
# ExternalService::FailedToCreateError: failed to crud with external service覆盖#initialize Strategy
这是我在rails中使用过的最接近实现的策略。如上所述，它使用demodualize、underscore和humanize ActiveSupport方法。但这可以很容易地删除，就像在之前的策略中一样。
module ExternalService
class FailedCRUDError < ::StandardError
def initialize(service_model=nil)
super("#{self.class.name.demodulize.underscore.humanize} using #{service_model.class}")
end
end
class FailedToCreateError < FailedCRUDError; end
class FailedToReadError < FailedCRUDError; end
class FailedToUpdateError < FailedCRUDError; end
class FailedToDeleteError < FailedCRUDError; end
end控制台输出
begin; raise ExternalService::FailedToCreateError; rescue => e; e.message; end
# => "Failed to create error using NilClass"
begin; raise ExternalService::FailedToCreateError, Object.new; rescue => e; e.message; end
# => "Failed to create error using Object"
begin; raise ExternalService::FailedToCreateError.new(Object.new); rescue => e; e.message; end
# => "Failed to create error using Object"
raise ExternalService::FailedCRUDError
# ExternalService::FailedCRUDError: Failed crud error using NilClass
raise ExternalService::FailedCRUDError.new(Object.new)
# RuntimeError: ExternalService::FailedCRUDError using Object演示工具
这是一个演示，展示了上述实现的救援和消息传递。引发异常的类是Cloudinary的假API。只需将上述策略之一转储到您的rails控制台，然后执行以下操作。
require 'rails' # only needed for second strategy
module ExternalService
class FailedCRUDError < ::StandardError
def initialize(service_model=nil)
@service_model = service_model
super("#{self.class.name.demodulize.underscore.humanize} using #{@service_model.class}")
end
end
class FailedToCreateError < FailedCRUDError; end
class FailedToReadError < FailedCRUDError; end
class FailedToUpdateError < FailedCRUDError; end
class FailedToDeleteError < FailedCRUDError; end
end
# Stub service representing 3rd party cloud storage
class Cloudinary
def initialize(*error_args)
@error_args = error_args.flatten
end
def create_read_update_or_delete
begin
try_and_fail
rescue ExternalService::FailedCRUDError => e
e.message
end
end
private def try_and_fail
raise *@error_args
end
end
errors_map = [
# Without an arg
ExternalService::FailedCRUDError,
ExternalService::FailedToCreateError,
ExternalService::FailedToReadError,
ExternalService::FailedToUpdateError,
ExternalService::FailedToDeleteError,
# Instantiated without an arg
ExternalService::FailedCRUDError.new,
ExternalService::FailedToCreateError.new,
ExternalService::FailedToReadError.new,
ExternalService::FailedToUpdateError.new,
ExternalService::FailedToDeleteError.new,
# With an arg
[ExternalService::FailedCRUDError, Object.new],
[ExternalService::FailedToCreateError, Object.new],
[ExternalService::FailedToReadError, Object.new],
[ExternalService::FailedToUpdateError, Object.new],
[ExternalService::FailedToDeleteError, Object.new],
# Instantiated with an arg
ExternalService::FailedCRUDError.new(Object.new),
ExternalService::FailedToCreateError.new(Object.new),
ExternalService::FailedToReadError.new(Object.new),
ExternalService::FailedToUpdateError.new(Object.new),
ExternalService::FailedToDeleteError.new(Object.new),
].inject({}) do |errors, args|
begin
errors.merge!( args => Cloudinary.new(args).create_read_update_or_delete)
rescue => e
binding.pry
end
end
if defined?(pp) || require('pp')
pp errors_map
else
errors_map.each{ |set| puts set.inspect }
endStack Overflow用户
发布于 2013-04-19 22:20:05
你的想法是对的，但你说它的方式是错的。它应该是
raise MyCustomError.new(an_object, "A message")页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/16106645
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