metaclasses

For instance, it took us a few months to understand how to use metaclasses, but a few years to understand how not to use them.

We explain the concept of composition of metaclasses.

Of course, the guilt of the authors is obvious here: our earlier installments on metaclasses in Python helped popularize their usage.

Each of these metaclasses has attributes from which Class inherits.

The metaclasses being extended by the stereotype are specified on the Extensions tab in the Properties view.

When you select multiple metaclasses, a generic features window opens where you can change the stereotype.

Notice that metaclasses were never mentioned in the lookup procedure.

A profile defines a number of stereotype classes that can extend one or more UML metaclasses with additional properties and relationships.

You feel that a custom metaclasses is overkill for the simple job of class initialization, and you would rather use a simpler solution.

Just this is the main difference between metaclasses and superclasses.

For metaclasses in Python specifically, Guido van Rossum's essay, Unifying types and classes in Python 2. 2 is useful.

Metaclasses are more fragile than many people realize.

Stereotype S1 has two attributes (a1: Integer, and a2 : Boolean), extends Class and Actor metaclasses, and has constraint profileCons1.

I have some ideas for doing some tricky stuff with metaclasses in future library versions, and I might even work in properties and slots.

Metaclasses defined in the UML 2. 1 metamodel (through metaclass association)

If the Duke class should happen to have a custom metaclasses, it can obtain some attributes that way