[Seaside] Dynamic typing in smalltalk

Sebastian Sastre sebastian at flowingconcept.com
Fri Oct 29 17:30:00 UTC 2010


It doesn't matter. You don't need to know the type. You need to know what to ask. 

For example its description (or label or whatever). So, you get a bunch of PaperBibli (and siblings) and you know they all answer correctly to, say, the #describe method. Then you use it (to render it or whatever).

That means you need to implement the #describe (or #description, or #name) method in every one of the subclasses (or factor it in its superclass)

sebastian
 


On Oct 29, 2010, at 2:43 PM, Alexandre BP wrote:

> thank you for your reply
> I have a class named "PaperBibli" which keeps a list of bibliographic entries.
> Those entries are of different type: Article, Book, Conference,...
> Every type has its own fields such as: author,title,...
> 
>  --> I created SubClasses of "PaperBibli" for each type so that when I instanciate an bibliographic entry I don't have lots of variables(fields) which are empty because not required in a particular type.
> The problem is that when I instanciate my bibliographic entry I still don't know of which type it is because the user tell me so by choosing in a scroll list.
> 
> I hope that my explanation is clear
> 
> 
> 
> 
> Date: Fri, 29 Oct 2010 12:24:22 -0400
> Subject: Re: [Seaside] Dynamic typing in smalltalk
> From: sean at monkeysnatchbanana.com
> To: seaside at lists.squeakfoundation.org
> 
> There are types in smalltalk. Each object has a type.
> 
> That aside, what are you trying to accomplish with your example below?
> 
> 
> On Fri, Oct 29, 2010 at 12:13 PM, Alexandre BP <abalonpe at ulb.ac.be> wrote:
> 
> Hello,
> 
> I would like to know if it is possible to apply dynamic typing in smalltalk. For example, If I want to use polymorphism, it would be:
> 	
>       var := Class new.
> 	var := (SubClass1) message. 
> 	var := (SubClass2) message.
> 
> Where message from SubClass1 is different then the one from SubClass2.
> Is there any solution for my problem? 
> I know that there is no type in smalltalk but there is definitely a way to use polymorphism right?
> 
> Thank you in advance,
> Regards
> alex
> 
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