extending STON

Henry,

> On 14 Nov 2017, at 15:02, henry <[hidden email]> wrote:
>
> Hello, I am trying to extend STON to allow for substitutions as data is written out or read in. On the write side I got it working as #nextPut: is recursively called, so that is the perfect place to substitute before an object is written. I have tested and my changes work well, where I have an arbitrary object as a subObject and it gets substituted out for my Descriptor object.

OK good.

> I am having difficult on the read side identifying where a substitution lookup should occur after decoding the object on the input stream. I want to inflate the Descritpor object, with its data, and call for a possible substitution. As it is a Descriptor, it should get substituted with the right bits on the read side. I chose to try and do this in the method #setReference:to: and put the substitute into the objects list. This did not work. Where is a good place to look within STON to do a read-side post-substitution?

In

STONReader>>#parseObject
        | targetClass reference object |
        [
                reference := self newReference.
                targetClass := self parseClass.
                object := targetClass fromSton: self.
                self setReference: reference to: object ]
...

I would try just re-assigning object with your custom substitute. Like this

MySTONReader>>#parseObject
        | targetClass reference object |
        [
                reference := self newReference.
                targetClass := self parseClass.
                object := targetClass fromSton: self.
                object := object resolveSubstitution.
                self setReference: reference to: object ]
...

The references are used if the same (#==) object is used twice, then you get something like

STON fromString: '[Point[1,2],@2]'.

which is an 2 element Array where the exact same object is in both positions (structure sharing). This works with circular references too (but be careful because the inspector might loop).

HTH,

Sven

> Thank you.
>
> - HH
>
>

Thank you, Sven. That was a much better place for internalizing after reconstituting. I now have bi-directional substitutions working with STON. I’m grateful.