异常处理

使用raise抛出异常

raise "OH NO!"
raise Exception.new("Some error")
# 继承Exception类可以自定义异常类
class MyException < Exception
end

处理异常使用rescue

begin
  raise "OH NO!"
rescue
  puts "Rescued!"
end
# 获取异常信息可以在rescue后加一个参数
begin
  raise "OH NO!"
rescue ex
  puts ex.message
end
# Output: OH NO!
# 捕获自定义异常
begin
  raise MyException.new("OH NO!")
rescue MyException
  puts "Rescued MyException"
end
begin
  raise MyException.new("OH NO!")
rescue ex : MyException
  puts "Rescued MyException: #{ex.message}"
end

如果没有捕获到任何异常，可以使用else

begin
  something_dangerous
rescue
  # execute this if an exception is raised
else
  # execute this if an exception isn't raised
end

ensure, 不管有无异常 都会执行

begin
  something_dangerous
rescue
  # ...
else
  # ...
ensure
  # this will always be executed
end