[Newbies] Creating a Class>>newX method directly from a pre-existing instance X

Chris Cunnington smalltalktelevision at gmail.com
Sat Jun 9 21:37:42 UTC 2012

Well, I don't think you'd programmatically create a new class, because your instance has to have been an instance of a class that already exists. Or else you would not have an instance to begin with. 

Perhaps, you want a way to programatically reproduce an instance you've been working with by hand in a Workspace. You have the instance. It's just right. You want it to be programmatically reproducible at will. I'd use Object>>storeString. 

x := (HelloWorld new) color: 'Black'.

I've created a instance with an instvar. I send it storeString:
x storeString 

and I get: 

'(HelloWorld basicNew instVarAt: 1 put: ''Black''; yourself)'

It's a bit crufty to me. I remove the first and last quote and parentheses. The double single quotes aren't great, so I remove them too. 

HelloWorld basicNew instVarAt: 1 put: 'Black'; yourself

Print it, and get: 

a HelloWorld 

I'm not sure why it comes in some extra syntax. 
That's my best guess at an answer to your question. YMMV. 


On 2012-06-09, at 5:04 PM, Erich Groat wrote:

> Hi all,
> I was wondering if there are any built-in facilities for taking a particular instance a class X, call it anX, and creating from it a class method that returns an identical instance of anX for future use.
> For example, say I'm futzing around in a workspace with an instance of a class called InteractiveWindowShape, tweaking things so that I have a nice window with all the colors and proportions and buttons I want, perhaps using Morphs to create the thing dynamically (so it's some kind of Morph object). In the course of this I get an instance of anInteractiveWindowShape that I am satisfied with, all the instance variables set just right. Let's call this object | idealShape |. It's just sitting there, rather vulnerably, in a workspace, the result of my using various screen tools over the last half hour. Now, I don't just want to save this object: I want to be able to create an identical one whenever I like. So what I want is a Class method, InteractiveWindowShapes class>>newIdealShape, that creates an instance exactly like idealShape.
> Is there a message I can send to this instance idealShape that would return a block of code that would act as a class method, which I could then call newIdealShape, and which would return an identical instance?
> I suspect such a general method might not exist, due to the potential hazards surrounding the deep copy problem; I also suspect I may not be imagining the best sort of solution to my problem. Is there a strategy for this?
> Thanks all!
> Erich
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