Re: How to make a class an alias of another one?
Mark Space wrote:
Lew wrote:
This gives the appearance of an antipattern: one should not hardcode
subclasses into their parent classes.
Given the simplicity of the request, I didn't see the need to make a
third class whose function was just a factory for ClassA and subclasses.
Gold plating -- needlessly complex design -- is an anti-pattern too. If
refactoring is required later, well, refactor. It happens.
Hence the part where I said, "gives the appearance of".
I thought your example was a good laboratory for the types of pragmatic
choices one makes knowing the consequences of those choices. Of course, that
makes it important to be aware of the consquences.
What safety there is in this use lies in that 'Temporary' is
package-private. This isn't completely safe, in that other subclasses
of 'A' can do Bad Things.
Isn't this a danger for all non-final classes? Any class can subclass
another non-final class, do bad things, break contracts, throw spurious
RuntimeExceptions, etc. Given that ClassA must be public and
extensible, I don't see a way around this.
I suppose that just making ClassA concrete and final would be ok, but if
one is planning on making changes later, it seems like having a defined
interface would be handy. I originally had ClassA as an interface, then
decided it needed a simple factory method. Hence, abstract.
More excellent thinking to take consequences into account.
You beautifully illustrate how careful compromises actually are better than
seeking the One Right Way.
--
Lew