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:pharo-users-bounces@lists.pharo.org] De la part de Steven Costiou
Envoy�� : mercredi 7 juin 2017 14:54
�� : 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.


!!!*************************************************************************************
"Ce message et les pi��ces jointes sont confidentiels et r��serv��s �� l'usage exclusif de ses destinataires. Il peut ��galement ��tre prot��g�� par le secret professionnel. Si vous recevez ce message par erreur, merci d'en avertir imm��diatement l'exp��diteur et de le d��truire. L'int��grit�� du message ne pouvant ��tre assur��e sur Internet, la responsabilit�� de Worldline ne pourra ��tre recherch��e quant au contenu de ce message. Bien que les meilleurs efforts soient faits pour maintenir cette transmission exempte de tout virus, l'exp��diteur ne donne aucune garantie �� cet ��gard et sa responsabilit�� ne saurait ��tre recherch��e pour tout dommage r��sultant d'un virus transmis.

This e-mail and the documents attached are confidential and intended solely for the addressee; it may also be privileged. If you receive this e-mail in error, please notify the sender immediately and destroy it. As its integrity cannot be secured on the Internet, the Worldline liability cannot be triggered for the message content. Although the sender endeavours to maintain a computer virus-free network, the sender does not warrant that this transmission is virus-free and will not be liable for any damages resulting from any virus transmitted.!!!"