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Cannot use slot as class variable: Raise explicit error #4314

jecisc opened this issue Aug 13, 2019 · 2 comments


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commented Aug 13, 2019

I tried to make BalloonEngine class variables BufferCache a WeakSlot but I got an error:

WeakSlot(Object)>>doesNotUnderstand: #asClassVariable
[ :e | e asClassVariable ] in ShiftClassBuilder>>sharedVariables: in Block: [ :e | e asClassVariable ]
[ :builder | 
	name: aSubclassSymbol;
	superclass: self;
	slots: slotDefinition;
	sharedVariables: classVarDefinition;
	sharedPools: someSharedPoolNames;
	category: aCategorySymbol ] in Object class(Class)>>subclass:slots:classVariables:poolDictionaries:package: in Block: [ :builder | ...
ShiftClassInstaller class>>make:
Object class(Class)>>subclass:slots:classVariables:poolDictionaries:package:

This might interest you @MarcusDenker


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commented Aug 14, 2019

Class Variables and Slots are two different entities: You can not use a Slot as a class variable.

(this might be possible to unify later, but even then this unified variable would need to implement different code for both the slot or the class var case and might be done via some additional layer,
the objects representing a variable inside an object vs. one in the class will have to be different as their API is different and the data they need is different....)

This means, if you want to have a "Weak Class Variable" you have to implement this, see ExampleClassVariable as an example.

I will add code to detect when people try to use slots as class vars and raise a nice error message.

@MarcusDenker MarcusDenker changed the title Cannot use slot as class variable Cannot use slot as class variable: Raise explicit error Aug 14, 2019


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commented Aug 14, 2019

Sadly I can not commit as my image does not allow me to make PRs (I press on "Ok" and nothing happens)

What needs to be done: add this method to Slot:

self error: 'Slots can not be used to define Class Variables, you need to create a LiteralVariable subclass instead'

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