[Bioc-devel] Error during wrapup, what does this mean?

[Robert Gentleman]

Dipl.-Ing. Johannes Rainer wrote:
> i agree with this. but what if the user types <ctrl>+c during the call? 
> i assume that try and tryCatch will not work in this cases, as i want 
> also roll back a transaction when the user breaks the operation by himself.
> currently i have solved the problem in the following way:
> with options(error=expression(.rollItBack()))

Hi,
  First - why assume, why not just test? Second - pass a connection in 
and use on.exit? Third, from the man page for tryCatch:
    User interrupts signal a condition of class 'interrupt' that
      inherits directly from class 'condition' before executing the
      default interrupt action.

  Which seems to answer your question.

> 
> and during the function call i copy the connection parameter to a global 
> variable called 'ErrorConnection' which is used by the rollItBack 
> function. on the 'on.exit' i reset the options(error=NULL) and remove 
> the 'ErrorConnection' from the global environment...

  And as I said - any and every error rolls back a transaction - not 
really what you would like to have happen. Using global variables is, in 
my experience, never a good idea. Explicity parameter passing, and 
encapsulation via lexical scope are much easier to work with.

  And what if I, as many other do, use options(error=recover) for 
debugging purposes. Your code seems to have a rather unfelicitous effect.

  Robert

> 
> jo
> 
> Quoting Robert Gentleman <rgentlem at fhcrc.org>:
> 
>> James W. MacDonald wrote:
>>
>>> Dipl.-Ing. Johannes Rainer wrote:
>>>
>>>> hi, it's again me, but i found the problem...
>>>> as i am working with database connections and if an error occurs in 
>>>> a function call i want to roll back the whole stuff that has been 
>>>> written into a database, i thought to be smart and defined with
>>>>
>>>>> options(error=expression(.rollItBack(Con)))
>>>>
>>>>
>>>>
>>>>
>>>> where .rollItBack is a function that sends the command ROLLBACK 
>>>> TRANSACTION to the database. well, i did not think, that when the 
>>>> error occurs the object Con, which is a local variable in the 
>>>> function does not exist, unless the user has called the connection 
>>>> object also 'Con'.
>>>>
>>>> now i want to ask how i can define a global variable from within a 
>>>> function.
>>>
>>>
>>>
>>> See ?"<<-" and ?assign
>>>
>>> HTH,
>>>
>>> Jim
>>>
>>
>> Hi,
>>
>>   But it is generally not a good idea to do it that way. If users have 
>> connections that you are using then they should be parameters to the 
>> functions that you are using and using try, or tryCatch, will 
>> generally be much better. I would also like to point out that if I 
>> understand this, then any error the user makes will roll-back a 
>> transaction - typing the wrong name for a function etc. That is 
>> probably not a good design decision.
>>
>>   Robert
>>
>>
>>
>>>
>>>>
>>>> cheers, jo
>>>>
>>>> Quoting "Dipl.-Ing. Johannes Rainer" <johannes.rainer at tugraz.at>:
>>>>
>>>>> hi,
>>>>> i am getting the error message:
>>>>>
>>>>>> Error during wrapup: Object "Con" not found
>>>>>
>>>>>
>>>>>
>>>>>
>>>>> in my functions and have no idea from where this message comes (i 
>>>>> have renamed some function arguments from 'Con' to 'con', maybe the 
>>>>> message comes from there :) ). nevertheless i do not know where i 
>>>>> should search for this error (as the functions work like they 
>>>>> should...). can anybody tell me more to this error message?
>>>>>
>>>>> cheers, jo
>>>>>
>>>>> _______________________________________________
>>>>> Bioc-devel at stat.math.ethz.ch mailing list
>>>>> https://stat.ethz.ch/mailman/listinfo/bioc-devel
>>>>>
>>>>
>>>> _______________________________________________
>>>> Bioc-devel at stat.math.ethz.ch mailing list
>>>> https://stat.ethz.ch/mailman/listinfo/bioc-devel
>>>
>>>
>>>
>>>
>>
>>
> 
> 
>