[IGSTK-Developers] Get method possibilities

[Luis Ibanez]

Hi David,

Thanks for posting the alternative options
for implementing the unsafe Get() methods.

--

What would be your preference between the
options:


     1) Adding FileSuccessfullyRead()
        removing the booleans and adding
        the [const std::strings &] on return.

or


     3) Throwing Exceptions when the
        values are not available.



[ Option (2) is the current one,
   so I would guess it is not int the list.
   The purpose of having the boolean to be
   returned by the same Get method was to
   ensure that the precondition and the action
   were performed as an atomic operation, but
   I agree with you in that we should not use
   any code that resembles FORTRAN. ]


--

Given that the Get() methods are now tagged and
recorded in the Logger, we could easily go with
any of the three proposed alternatives, since
none of those is quite fit for a State Machine
architecture anyways.


We just need to pick up the one that will reduce
the developer's effort to a bare minimum, make
them feel more comfortable, and provide them with
the maximum of flexibility.


Please let us know what would be your preference
so we can make these changes today before moving
the code to the main IGSTK library.


   Thanks


      Luis


-------------------
David Gobbi wrote:
> Hi All,
> 
> The ImageReader Get methods that were just added to CVS are a
> bit clunkier than I would like,  due to the boolean return value.  In
> VTK and ITK, the methods would return the string (or a const
> reference to the string) and forgo the boolean return value.
> 
> Typical VTK/ITK code looks like this:
> 
> if (reader->FileSuccessfullyRead())
> {
> std::string   patientName = reader->GetPatientName();
> std::string   patientID = reader->GetPatientID();
> std::string   modality = reader->GetModality();
> 
> .. plus additional code to process the information
> }
> ... at this point in the code, the patientName, patientID, and modality
>   variables are no longer in scope, so there is no danger of them being
>   used if the file hasn't been read yet.
> 
> With the methods that were just added (with the boolean return value),
> the code will look like this:
> 
> std::string patientName;
> if (reader->GetPatientName(patientName))
>  {
>   ... use the patient name
>  }
> std::string patientID;
> if (reader->GetPatientID(patientID))
>  {
>  ... use the patient ID
>  }
> ... and so on for modality
> 
> ... at this point in the code, the "patientName", "patientID", and 
> "modality"
>   variables are all still in scope, even if the Get() methods failed.  
> This sort
>   of a programming pattern reminds me of FORTRAN.
> 
> Just my two cents.
> 
> - David
> 
> P.S. I can't resist adding an example that uses exceptions:
> 
> try
>   {
>   std::string   patientName = reader->RequestPatientName();
>   std::string   patientID = reader->RequestPatientID();
>   std::string   modality = reader->RequestModality();
>   .. plus additional code to use the information, not executed if an 
> exception occurs
>   }
>  catch (InvalidRequest)
>   {
>   ... send debug info to logger
>   }
> 
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