[Uml-devel] kdesdk/umbrello/umbrello

[Andrew Sutton]

On Monday 24 February 2003 3:01 pm, Mathias Meyer wrote:
>
> > They're called Paramaterised Classes in UML.  Java calls the
> > Generics, or will do when they exist.
>
> I meant the XMI/UML DTD not UML in general. I was really looking forward
> to having support for them in Umbrello and now here we are, looking
> better than Argo and Poseidon ;)
> One obvious way to come around the template problem are stereotypes, but
> why use them when there's support for templates in UML.

the 2.0 object model supports them alread :) of course, the 2.0 UML object 
model is also around 500 classes. not that this has any bearing on what 
you're talking about, i just thought i'd throw that out there... ;)

actually, they aren't REALLY called parameterized classes. you can 
theoretically paramaterize almost anything UML (like operations, states, use 
cases). i'm not sure how much sense that makes, but its possible. anyways, 
the result of defining template parameters for a class makes it a 
parameterized class - they don't really exist by themselves.

on a related note - if anybody's going to do any work for this - here's how 
templates in UML are supposed to work. something (lets call it UMLClass in 
this case) has a list of template parameters. if that list is NOT empty, then 
the UMLClass becomes a "template". i.e., it cannot be used like a regular 
class (can't be used in inheritance or as types of other objects like 
attributes or parameters). you have to define a special object called a 
"binding" (or UMLBinding) that contains values for the template parameters of 
the template class. this new object (the UMLBinding) can then be used like a 
regular class. does that makes sense?

put another way, if a class has template parameters, you can't use it - just 
like you can't use C++ templates without arguments for the parameters. the 
act of creating the binding is similar to a typedef in C++:

typedef std::list<std::string> StringList;

now i can use StringList like a class.

if somebody were actually going to implement this, here's what i'd suggest for 
XMI storage: use the same (or similar) mechanism as how you store parameters 
for a method. as for the UMLBinding object, you could just store arguments to 
the template parameters as strings - i don't think it would need to be much 
more complex than that.

> Are those Generics a planned feature for Java? And is the whole world
> programming Java or what? ;)))

yes. apparently, we've all missed the boat :) i think what jonathan is 
describing is the inclusion of template programming (i.e., generic 
programming) into the java language.

andy