单个异常使用 fail 关键字仅仅当捕获一个异常并且反复抛出这个异常(因为这里你不是失败，而是准确的并且故意抛出一个异常)。
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begin fail 'Oops'rescue => error raise if error.message != 'Oops'end |
不要为 fail/raise 指定准确的 RuntimeError。
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# bad fail RuntimeError, 'message' # good - signals a RuntimeError by default fail 'message' |
宁愿提供一个异常类和一条消息作为 fail/raise 的两个参数，而不是一个异常实例。
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# bad fail SomeException.new('message') # Note that there is no way to do `fail SomeException.new('message'), backtrace`. # good fail SomeException, 'message' # Consistent with `fail SomeException, 'message', backtrace`. |
不要在 ensure 块中返回。如果你明确的从 ensure 块中的某个方法中返回，返回将会优于任何抛出的异常，并且尽管没有异常抛出也会返回。实际上异常将会静静的溜走。
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def foo begin fail ensure return 'very bad idea' end end |
Use implicit begin blocks when possible.如果可能使用隐式 begin 代码块。
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# bad def foo begin # main logic goes here rescue # failure handling goes here end end # good def foo # main logic goes here rescue # failure handling goes here end |
通过 contingency methods 偶然性方法。 (一个由 Avdi Grimm 创造的词) 来减少 begin 区块的使用。
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# badbegin something_that_might_failrescue IOError # handle IOErrorendbegin something_else_that_might_failrescue IOError # handle IOErrorend# gooddef with_io_error_handling yieldrescue IOError # handle IOErrorendwith_io_error_handling { something_that_might_fail }with_io_error_handling { something_else_that_might_fail } |
不要抑制异常输出。
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# badbegin # an exception occurs hererescue SomeError # the rescue clause does absolutely nothingend# baddo_something rescue nil |
避免使用 rescue 的修饰符形式。
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# bad - this catches exceptions of StandardError class and its descendant classes read_file rescue handle_error($!) # good - this catches only the exceptions of Errno::ENOENT class and its descendant classes def foo read_file rescue Errno::ENOENT => ex handle_error(ex) end |
不要用异常来控制流。
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# bad begin n / d rescue ZeroDivisionError puts "Cannot divide by 0!" end # good if d.zero? puts "Cannot divide by 0!" else n / d end |
应该总是避免拦截(最顶级的) Exception 异常类。这里(ruby自身)将会捕获信号并且调用 exit，需要你使用 kill -9 杀掉进程。
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# badbegin # calls to exit and kill signals will be caught (except kill -9) exitrescue Exception puts "you didn't really want to exit, right?" # exception handlingend# goodbegin # a blind rescue rescues from StandardError, not Exception as many # programmers assume.rescue => e # exception handlingend# also goodbegin # an exception occurs hererescue StandardError => e # exception handlingend |
将更具体的异常放在救援（rescue）链的上方，否则他们将不会被救援。
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# badbegin # some coderescue Exception => e # some handlingrescue StandardError => e # some handlingend# goodbegin # some coderescue StandardError => e # some handlingrescue Exception => e # some handlingend |
在 ensure 区块中释放你程式获得的外部资源。
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f = File.open('testfile') begin # .. process rescue # .. handle error ensure f.close unless f.nil? end |
除非必要, 尽可能使用 Ruby 标准库中异常类，而不是引入一个新的异常类。(而不是派生自己的异常类)
