[squeak-dev] What are the current use cases for traits? (was: The Inbox: TraitsTests-pre.19.mcz)

Levente Uzonyi leves at caesar.elte.hu
Sun Mar 31 19:20:47 UTC 2019

On Sat, 30 Mar 2019, David T. Lewis wrote:

> Changing the subject line to focus on Levente's question.
> On Thu, Mar 28, 2019 at 06:43:11PM +0100, Levente Uzonyi wrote:
>> What are the current use cases for traits?
> In order to experiment with Git based repositories, I have loaded the
> Tonel package from the github repositories of Jakob Reschke.
> 	Installer ensureRecentMetacello.
> 	(Smalltalk classNamed: #Metacello) new
> 	   repository: 'github://j4yk/tonel:squeak';
> 	   baseline: 'Tonel';
> 	   load.
> This brings in the FS-AnsiStreams package, which uses traits.
> Having traits in Squeak allows me to load this package.

I haven't tried your snippet and I don't know which version of FS depends 
on Traits, but the one on SqueakSource definitely does not.
Btw, Traits can be flattened, so it's possible to make it loadable into 
images with no Trait support.

So far all use cases of Traits in this thread (and its parent) were about 
interfaces. Squeak doesn't have a concept for that, and Traits are 
definitely more than just simple interfaces (as long as you don't want to 
interface state). Perhaps we need interfaces instead of traits.


> Dave

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