Cache of the mapping is just an implementation detail. I was referring to the instance of the ==MyRectangle== object; so I am more interested in this from outside perspective --- other objects that will have to use the API... So whether I would call [[[ "class-side methods" MyRectangle oppositeSideOf: #top "-> #bottom" "instance side" MyRectangle new oppositeSideOf: #top "singleton" MyRectangle instance oppositeSideOf: #top "extending symbols" #top oppositeSide "a lot of classes" Top "new/instance/whatever" oppositeSide "-> a Bottom instance/class" " or something (completely) different?" ]]] Peter On Thu, Jul 23, 2015 at 2:18 PM, Ben Coman <btc@openinworld.com> wrote:
Even if you put the method on the class-side, you would still be creating an new instance each time. Maybe you can store it in a class variable...
MyRectangle>>oppositeSides ^ oppositeSides ifNil: [ oppositeSidesCache := { #top -> #bottom. #bottom -> #top. #topLeft -> #bottomRight .... } asDictionary ].
cheers -ben
On Thu, Jul 23, 2015 at 8:40 AM, Peter Uhnak <i.uhnak@gmail.com> wrote:
Hi,
I am trying to figure out where to best place some mapping/data/stable methods.
For example imagine method ~~~~~~~~~~~~~~~~~~~~~ MyRectangle>>oppositeSides ^ { #top -> #bottom. #bottom -> #top. #topLeft -> #bottomRight .... } asDictionary ~~~~~~~~~~~~~~~~~~~~
And then the class might have some other related methods such as ~~~~~~~~~~~ MyRectangle>>oppositeSideFor: aSide ^ self oppositeSides at: aSide ~~~~~~~~~~~~
So it's a method returning a mapping between opposite sides/corners and thus is really not going to change. Now I could place this in instance-side and create a new instance every time I wanted to use it (which doesn't seem practical), or I could put it in class-side. The problem I have with class-side is that naming is more like going through minefield (more than once I corrupted my image by naming a method or variable something I shouldn't have), and for whatever reason it feels like either metaprogramming or procedural programmming... That class side methods are pretty much global functions/variables... and short of constructors I am avoiding static methods even in other languages... but maybe using it is ok. Or maybe have it object an use singleton?
The only oop-like approach I see would be to extend symbols (#top oppositeSide), or have separate objects for sides, but that seems like overkill.
MySide subclass: #Top
Top>>oppositeSide ^ Bottom new
Are there any best practices regarding this? This is also true for actual data stored in methods/attributes (such as icons).
P.s.: For english natives... Should the second method be ned "oppositeSideOf:" or "oppositeSideFor:"?
Any ideas/pointers appreciated, Peter