# Error: Called id for nil, which would mistakenly be 4

**URL:** <https://www.ruby-forum.com/t/error-called-id-for-nil-which-would-mistakenly-be-4/158254>\
**Category:** Rails\
**Created:** [January 21, 2009, 3:53am UTC](https://www.ruby-forum.com/t/error-called-id-for-nil-which-would-mistakenly-be-4/158254 "2009-01-21T03:53:29Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![youhaodeyi](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/y/b9bd4f/32.png) [@youhaodeyi](https://www.ruby-forum.com/u/youhaodeyi)\
**Post date:** [January 21, 2009, 3:53am UTC](https://www.ruby-forum.com/t/error-called-id-for-nil-which-would-mistakenly-be-4/158254/1 "2009-01-21T03:53:29Z")

</div>

I define a class:

class BuildLogger  
@@build\_logger=nil

def self.get\_build\_logger(file\_name=nil)  
if @@build\_logger == nil ###this line will thrown an error  
@@build\_logger=Logger.new(“build\_logger”)  
@@build\_logger.level = DEBUG  
end  
return @@build\_logger  
end  
end

I invoke BuildLogger.get\_build\_logger in a controller. An error “Called  
id for nil, which would mistakenly be 4 – if you really wanted the id  
of nil, use object\_id” is always thrown on the “if” line. I have no idea  
about this error. does anyone know this problem?