> On 3 Apr 2019, at 15:57, Vitor Medina Cruz <vitormc...@gmail.com> wrote:
>
> Hello,
>
> Is it possible to intercept a slot store? I tried with a before metalink into
> #write:to selector, but it don't seems to work. Should I use another selector?
>
The #write:to: method is the reflective read method that implements read on the
level of the variable. If you subclass class Slot, you can make you own kind of
Variables by just overriding #write:to and read:
But of course compiling every read by calling a method would be very slow.
Therefore, one can override emitStore: and emitValue: to instead emit faster
code by telling the compiler exactly what bytecode to generate for read and
write.
This makes it much faster, but at the expense that the reflective methods are
not called anymore.
(It would be nicer if we would inline the read: code automatically, but that
has its own set of problems)
> I would like to experiment with ivar change notification, but I don't know
> what is the better approach.
>
What you could do is to make your own subclass to experiment. IndexedSlot is
the superclass of the normal instancevariables, but without the optimised code
generation.
So it is the perfect superclass to experiment:
IndexedSlot subclass: #MyTestSlot
instanceVariableNames: ''
classVariableNames: ''
package: 'Slot-Core-Variables’
now Implement
read: anObject
Transcript show: 'reading ', self name.
super read: anObject.
Now we can make a class that uses it:
Object subclass: #MyClass
slots: { #ivar => MyTestSlot }
classVariables: { }
package: 'Slot-Core-Variables’
and add a simple method reading the variable:
ivar
^ivar
If you now execute "MyClass new ivar” and you will see the output on the
Transcript.
Marcus
