Hi Offray,
This is a recurring question. BlockClosures are way too general and powerful to
be serialised. That is why serialising BlockClosures is not supported in STON.
The code inside a block can refer to and even affect state outside the block.
Furthermore the return operator is quite special as it returns from some outer
context.
A subset of BlockClosures are those that are clean. These do not close over
other variables, nor do they contain a return. By using their source code
representation, it is possible to serialise/materialise them.
You can try this by adding the following methods:
BlockClosure>>#stonOn: stonWriter
self isClean
ifTrue: [ stonWriter writeObject: self listSingleton: self printString ]
ifFalse: [ stonWriter error: 'Only clean blocks can be serialized' ]
BlockClosure>>#stonContainSubObjects
^ false
BlockClosure class>>#fromSton: stonReader
^ self compilerClass new
source: stonReader parseListSingleton;
evaluate
With these additions you can do the following:
STON fromString: (STON toString: [ :x :y | x + y ]).
Note that the actual class name depends on the Pharo version (BlockClosure in
Pharo 7, FullBlockClosure in Pharo 9 and maybe soon CleanBlockClosure - Marcus
is working on that last one and that would be very cool because it would say
exactly what it it).
I am still not 100% convinced to add this as a standard feature to STON. Using
source code fully exposes the implementation, while using the compiler can be
dangerous. It also adds a dependency on source code and the compiler. But it
would be good if people can experiment with this feature.
Does this help you ?
Regards,
Sven
PS: I would not modify an object just to serialise it.
> On 30 Nov 2020, at 18:19, Offray Vladimir Luna Cárdenas
> <offray.l...@mutabit.com> wrote:
>
> Hi,
>
> I'm using STON for all my light storage serialization needs, like the
> Grafoscopio notebooks, and I also love it, as Russ stated in their mail
> question, and I share with him a similar request: for my Brea[1] static
> site generator I would like to store some BreaQuery objects as external
> STON files, and recover them, so I can run the queries that
> recreate/update the website easily. I could store them as Grafoscopio
> notebooks, but I don't want to make Grafoscopio a prerequisite for Brea
> or I could use Fuel, but I would like to store queries as a diff
> friendly text based format. I have considered Metacello/Iceberg packages
> to export code in a diff friendly format, but It maybe overkill. So I
> would like to see if STON can serve me here too.
>
> [1] https://mutabit.com/repos.fossil/brea/
> [2] https://mutabit.com/repos.fossil/indieweb/
>
> So far, I'm able to serialize a code block as a string using:
>
> BreaQuery>>asStonModified
> self codeBlock: self codeBlock asString
> ^ STON toStringPretty: self
>
> But I'm unable to populate a block from a string. There is any way to
> make a string, lets say 'a + b', to become the code contents of a block,
> ie: [a + b ] ?
>
> Thanks,
>
> Offray
>
