On 03.06.14 08:03, stepharo wrote:
hi guys
I was reading a proposal that was sent to the list and I like it. What do you think?
Stef
Hi Otto,
Well, you asked for comments. This is my personal opinion, which varies quite a bit from most implementations, since it's a bit 'old-school Smalltalk'. But I think the scheme below does fairly neatly distinguish the purposes of the various messages, which have gotten muddied over the years as new developers use the language somewhat differently. But maybe it was never the way I think I remember it being. :-)
#printString and #printOn: These should answer a human-readable description of the receiver. The description does not need to include the class name, though it can. All objects should respond to these messages. Generally, #printString should be implemented in terms of #printOn: -- if you're writing to a stream you may not want to pay the cost of creating an extra string. #printString is the equivalent of other languages' toString().
#asString There should not be an Object>>asString. This message is *only* for converting string-like things to actual strings. So it would be implemented in String (to return self) and in Symbol, and *maybe* in things like ByteArray (where it does not *describe* the byte array, but answers a string whose characters have the values of the bytes).
#storeString Produces legal Smalltalk source code that when executed will produce an equivalent object to the receiver. Needs to be implemented only for objects that can be specified as literals in Smalltalk syntax, but could probably be implemented for a few other simple objects.
#displayString and so on. UI frameworks and applications will need to have their own ways of textually representing objects, so will add their own messages such as #displayString. The *only* messages that any application or framework can depend on *all* objects responding to are those that it defines itself, and #printString and #printOn:.
Sounds a lot like VW. I still remember the very complex rules we had in Seaside 2.x for when you should send #displayString, when #printString and when #asString. In the end we built #greaseString (#seasideString once) and everything became much simpler. Cheers Philippe