I managed to do it :) What i did not say is that the subclasses (with new inst var) i want to use are anonymous subclasses.
So i subclassed the SlotClassBuilder and i did: - generate an anonymous subclass from the source class - migrate my object - modify the anonymous subclass with new instance variables - rebuild the class with my own SlotClassBuilder It seems to work. I did not try how to migrate back my object to its original class but i think i might have a problem there. Also it seems very slow. Indeed it is a very certain, specific application :) Steven. Le 2017-06-07 15:32, Blondeau Vincent a écrit : > So, I do not think that is possible... > > Any solution I see is either to change the superclass or to add an external > object with a mapping between your new objects and the values of your new > IVs. > > Or you do the migration and after you add the IV once all instances are > migrated. > > But, I repeat that, as written in comments of primitiveChangeClassTo, "The > facility is really provided for certain, very specific applications (mostly > related to classes changing shape) and not for casual use." > > Vincent > > DE : Pharo-users [mailto:pharo-users-boun...@lists.pharo.org] DE LA PART DE > Steven Costiou > ENVOYÉ : mercredi 7 juin 2017 15:18 > À : Any question about pharo is welcome > OBJET : Re: [Pharo-users] How to migrate an object to a subclass of its class > but with new inst vars ? > > 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:pharo-users-boun...@lists.pharo.org] 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.
