[英]Ruby error: undefined method `casecmp' for nil:NilClass
我有以下代码(添加了一些调试行):
红宝石:
re_dict = {}
re_dict['state'] = 'pending' #set initial status to pending
puts re_dict, re_dict.class.to_s
puts re_dict['state'], re_dict['state'].class.to_s
puts re_dict['state'].casecmp('pending')
while re_dict['state'].casecmp('pending') == 0 do
stuff
end
产量
state: pending
state class: String
class compared to 'pending': 0
Completed 500 Internal Server Error in 66ms
NoMethodError (undefined method `casecmp' for nil:NilClass):
是什么原因造成的? 我如何失去哈希值?
仅当您从while循环内的re_dict
哈希中删除'state'
键时,才会发生这种情况:
while re_dict['state'].casecmp('pending') == 0 do
puts re_dict
re_dict = {}
end
#=> {"state"=>"pending"}
#=> NoMethodError: undefined method `casecmp' for nil:NilClass
由于键'state'
不再可用,因此调用re_dict['state']
会得到nil
,这就是为什么undefined method casecmp' for nil:NilClass
获取undefined method casecmp' for nil:NilClass
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