|If you have started working with distributed computing you will have seen
the following message:
Cannot convert any in Any variable to integer.
message is normally generated because you made a distributed call to a function with a
return value and the function failed. When your code is more thoroughly debugged the mean
time between messages is less but they still occur on a regular basis. One of the design
principle of our new class library was that just because a single window/Entity has a
problem that cannot be resolved such as this, then the whole application should not suffer
the consequences of a system error being generated. Instead just the part of the
application with the problems should be shutdown.
Our way of dealing with the problem is that the pattern that is link to the distributed
business entity should be shutdown (the windows will be closed), after giving the user a
nice friendly message.
Prevention is the best solution for system errors, thus we needed a way to protect the
patterns from ever generating this error. We have a single common interface between the
pattern and the business entity, all calls to the business entity are generated by user
interaction with patterns, these patterns make a service request which our interface knows
how to consume.
Whenever we make a call to a distributed entity that returns a value, we accept the
return value into an Any variable, then we check to see if the data type of the return
value is the correct type (usually an integer). If the data type is correct then we cast
it into the return value and continue processing. If the data type does not match then the
business entity failed and the user is told about the problem, the pattern and distributed
business entity are then closed.
This reason behind this is simple. If you export the syntax of a proxy you can see that
all the arguments and return values are cast to an any before and after the call is made.
Thus if the call fails the return value is not placed into the Any variable. So you are
returned a Null Any variable, thus when you assign it to an integer or other type you get
a visit from the system error!