Hi,
This is a bugbear for me.
On 2015/09/30 09:35 PM, Lyn Headley wrote:
Hello,
As I understand it, in Smalltalk, the instance variables of a class C
are "protected" - able to be referenced by methods of C or its
subclasses, but not by other objects. This is a useful feature as it
clearly points out which pieces of data are not available to other
objects, and thereby simplifies code.
However, I am often unsure of whether to use this feature or not, as
it conflicts in my mind with the practice of using accessor methods. I
like accessor methods because they make it easy to change behavior
later -- If I have a dozen calls to an accessor method, then I only
need to change it in one place. If these were instance variable
references, I would have to do more work. The disadvantage of accessor
methods is that they obscure the protected status of data -- it
becomes unclear how protected an instance variable is meant to be.
(Accessors also make it harder for me to find users of the data when
browsing, when there are senders from totally unrelated classes,
although I suspect I have just not figured out how to browse scoped in
the right way for this).
It occurs to me that a tool could be (easily?) developed that would
solve this problem. It would take existing variable references and
turn them into calls to accessor methods. That way, I could have
protection when I want it, and easy ability to change code as well.
Does something like this exist, or is it feasible to build?
How do others think about this issue?
-Lyn
I'm old-school OO and don't like accessor methods at all. They break
encapsulation, they cloud the object interface, and most importantly
they allow bugs to be introduced by undocumented modification of the
object's internal state.
Nobody has shown me a good reason for their existence and I never use
them except where I'm forced to use them in Spec and Glorp.
Craig
PS: I'm forced to use them in C# as well (my day job). Because in C#
it's only way to promote a local variable to a property which is
required by most frameworks.
