So I have the following case. I have an interface A and an implementation AImpl. Now I have another implementation of A, called A2Impl, which references any instance of A besides implementing A already.
So I have now drawn the following UML class diagram:
Would this be correct? How do i draws this correctly?
Yes, it is correct, but not optimal.
The dependency just says 'A2Impl' cannot do without 'A', but that is obvious, since A2Impl implements A. In fact, the 'implements' relationship implies the dependency.
If A2Impl has a permanent reference to another instance of A, it would be better to replace the dependency by an association (an arrow with a solid line instead of a dashed line). You may wish to add multiplicities to the association (not mandatory). In the figure below, I have specified multiplicity "1" to indicate that every instance of A2Impl always refers to exactly one instance of A.
If you think an association is not appropriate, you could also assign a stereotype to the dependency, to indicate the type of dependency, e.g. «call».
