On Wed, Sep 16, 2020 at 10:28 AM <s...@clipperadams.com> wrote:
> Stéphane Ducasse <stephane.duca...@inria.fr> wrote:
>
> refrain from using respondTo: I make code difficult to evolve and can
> introduce vicious bugs.
>
> Steph, would you say more about this? It’s something I’ve been wondering
> about.
>
> I was recently reading the Strategy pattern in the Smalltalk Companion to
> the GOF book. On p. 339, they proposed the following "Smalltalk way" as an
> alternative to the common class-per-strategy implementation:
>
> [[[language=smalltalk
>
> Composition>>repair
>
> "Without the strategy pattern, but using perform:."
>
> | selector |
>
> "Construct the name of the method to invoke:"
>
> selector := ('formatWith', formattingStrategy, 'Algorithm') asSymbol.
>
> self perform: selector
>
> ]]]
>
> It then dismissed the approach as "''clever but difficult from a program
> understanding perspective. Even static analysis tools such as code
> browsers' "senders" and "messages" fail on this code.''"
>
It is always best to have senders of the methods you use. Additionally,
it's far better to properly manage the user-friendly identification of a
thing and the thing itself. e.g. Plain language name mapped to a selector
or a block.
Remember, "the fact that one *can* do something is far different from
whether one *should* do that thing." (I have suffered far too often and far
too long from clever programs preferring the former without thinking about
the latter.)
It struck me as perhaps a bit extreme (i.e. too clever indeed) to construct
> the algorithm selector via string concatenation. Maybe "senders" search
> capabilities have gotten more sophisticated since publication, but Pharo
> seems to support symbol arguments, even for e.g. message renames. I
> thought, why not the following:
>
> [[[language=smalltalk
>
> Composition>>repair
>
> "Without the strategy pattern, but using perform:."
>
> self perform: self formattingStrategy
>
> ]]]
>
> Then client code like ==aComposition formattingStrategy:
> #formatWithSimpleAlgorithm== would show up in senders, message renames, etc.
>
> But from what you’re saying, I feel I may be missing something…
>
>
>
