Re: [Pharo-dev] Why String do not implement #displayString?

[Benoit St-Jean via Pharo-dev]

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In the "old" days, programmers made sure to respect the following conventions : 
you implement #storeOn:, #displayString: and #printOn: .  Eventually, an object 
will be sent #storeString and #printString and will use your #whateverOn: 
implementation.  
It looks like that good habit that I've learned at university looooooong ago 
got lost somewhere.  It looks like no one uses #displayString anymore and rely 
solely on #printString instead!  I had a teacher once telling me #displayString 
had a crappy implementation : it just sent #printString and that to be "code 
clean", one should implement #displayOn: and modify #displayString accordingly.
But if I recall, VW at the time introduced #displayOn: for widgets and other 
things, hence why #displayString never sent #displayOn:.
To make a long story short of what should have been and what it's always been, 
here's an excellent paper on the subject!
http://esug.org/data/HistoricalDocuments/TheSmalltalkReport/ST07/04wo.pdf

----------------- 
Benoît St-Jean 
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"A standpoint is an intellectual horizon of radius zero".  (A. Einstein) 

    On Tuesday, April 10, 2018, 11:28:57 a.m. EDT, Esteban A. Maringolo 
<emaring...@gmail.com> wrote:  
 
 Isn't #displayString implemented in terms of #displayOn: the same way
#printString is implemented in terms of "printOn:"?

And in the case of String #displayString should return the receiver (it
is, self), so the following should be true.

| s |
s := 'Hello, ''Funny'' World'.
s displayString = s. "true"
s printString = s. "false"

Regards,


On 10/04/2018 12:21, Denis Kudriashov wrote:
> Hi.
> 
> According to the comment of #displayString it should be used as default
> textual representation of objects in the UI:
> 
>    "While printString is about to give a detailled information about an
>    object, displayString is a message that should return a short
>    string-based representation to be used by list and related UI
>    frameworks. By default, simply return printString."
>    "asString should not be implemented in Object, and kept for
>    conversion between strings, symbols, text and characters."
> 
> But String itself does not respect this message:
> 
>    'some string' displayString " ==> '''someString''' "
> 
> 
> Is it bug? Or is there any reason for this?
> 
> Best regards,
> Denis

-- 
Esteban A. Maringolo

  

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