Hey,
there are some threads in this group hinting to special solutions in
cases where you want to have some kind of references build in - or on
top of - protobuf messages. For example you would want that to model
DAG (or even cyclic graph) structures.
I was thinking about how I would want such techniques to be
implemented/usable and came up with this:
For messages types A and B where A messages are supposed to have
references to B messages:
message A {
required int32 ownvalue = 1;
required ptr_B bref = 2;
}
message B{
required bytes UUID = 1;
required int32 othervalue = 2;
}
message ptr_B {
required bytes refUUID = 1;
}
where ptr_B obviously is a "reference variable message" to a specific
B message (where the join of cause is on refUUID and UUID).
So far this is no problem, as I can easily have a script generate
ptr_X messages for each message X containing a defined attribute (e.g.
"required bytes UUID").
The second part however is where I am not so sure. I would want to
have some type safe way of navigating/dereferencing those references.
Like:
A a; //this is what I received before
ptr_B reference = a.getRefUUID(); //get reference
B b = foo(reference); //dereference
A standard protocol buffer message type ptr_B from which a "flat" Java
class will be generated does not seem adequat to to so.
Instead some new abstract Class "RefMessage<T extends Message>" with a
method "<T> getReferencedObject()" would be the solution. ptr_X
messages simply had to be transformed to Java classes extending this
superclass.
My questions so far:
I could write my own code generator for that purpose, right?
Has anybody tried to implement some similar techniques for reference
types on top of protocol buffer?
Is there a completely different approach for this "problem"?
Am i getting the design and purpose of protobuf wrong when I need/want
such a solution?
Chris
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