Hi Vincent, thanks for your quick answer.
This is the default behavior of adoptInstance: which calls
primitiveChangeClassTo:
But i specifically want to gain new inst vars, which does not work that
way.
I can't add an instvar to the superclass since i don't want to change my
system.
Steven.
Le 2017-06-07 15:09, Blondeau Vincent a écrit :
> Hi,
>
> You should be able to do it using the method primitiveChangeClassTo: but it
> not recommended to do it. Are you sure that it is the only way to resolve
> your problem?
>
> If you really want to, an example:
>
> Object subclass: #Toto
>
> slots: { #tata }
>
> classVariables: { }
>
> category: 'Temp'.
>
> Toto subclass: #Titi
>
> slots: { }
>
> classVariables: { }
>
> category: 'Temp'.
>
> obj := Toto new.
>
> obj primitiveChangeClassTo: Titi new.
>
> obj has a new class.
>
> However, you cannot add a new instance variable this way but you keep the
> values of the instance.
>
> But nothing avoid you to add an empty instance variable in a superclass that
> only the subclass will use.
>
> I hope that it will help you
>
> Vincent
>
> DE : Pharo-users [mailto:[email protected]] DE LA PART DE
> Steven Costiou
> ENVOYÉ : mercredi 7 juin 2017 14:54
> À : Pharo users users
> OBJET : [Pharo-users] How to migrate an object to a subclass of its class but
> with new inst vars ?
>
> Hi,
>
> i'm trying to migrate an object from a given class A to a subclass of A with
> new inst vars. Can't get it to work.
>
> I have a class and an instance of it, say:
>
> Object subclass: #A
> instanceVariableNames: ''
>
> |a|
>
> a := A new.
>
> A has no instance variables. Now i create a subclass B of A with a new inst
> var:
>
> A subclass: #B
> instanceVariableNames: 'x'
>
> I want to do the following:
>
> B adoptInstance: a
>
> It does'nt work, for what i understand it is because the format of the
> classes are different (B has an inst var and A has not).
>
> How can i make the a object become an instance of B (subclass of a's class),
> making a acquiring the new inst var x (and in more complex cases keeping its
> own previous inst vars) ?
>
> Steven.
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