thmpsn....@gmail.com wrote
>> This allows people to meddle with internals, at their own risk,
>> if it ends up being absolutely necessary.
>
> If it ends up being necessary, the class's design is flawed. (Though
> in this case, the flaw is easily solved by simply providing a getter.)
No the class design is not necessarily flawed. Sometimes it is
desirable to modify a class's behavior at a lower level. In Java this
isn't possible directly and so it has led to an entire class of
libraries that provide means of doing this. For more information, look
up "Aspect-oriented Programming" on wikipedia. Since most
aspect-oriented programming examples I've seen are in Java I never
understood much about it ("cross-cutting concerns" is a pretty
meaningless explanation) until I realized that metaprogramming in
python, monkey-patching classes, and dynamically adding attributes to an
existing class are all forms of aspect-oriented programming. And it
turns out to be quite useful for some things.
One area where aspect-oriented programming is useful is in libraries
that add security layers to objects and methods. Rather than having to
make code directly aware of the security layer (which could take
different forms), we can instead reach into the classes and, for
example, wrap certain methods in a function that enforces security. If
we do it in the class directly, then even code that descends from this
class will transparently "inherit" all of the newly added security layer
code that was never there when the code was first written. By security
layer I'm talking more about code that enforces certain user
authentication before use (as in web programming) rather than "secure" code.
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