NeoJSON "conditional" parsing/mapping

Hi Sven, all,

I'm working on a JSON-RPC client, I started using LtJsonRpcClient, but
since it's based on the "legacy" JSON package I decided to try to
adapt it to use NeoJSON. So I created a NeoJSONRPCClient based on
LtJson... because... why not.

At its core JSON-RPC is a pretty simple protocol, every response is a
JSON object with a 'result' attribute holding the returned object from
the RPC call, an 'error' one (nil if no error happened), and a few
other ones [1].

If I convert the response using the traditional `NeoJSONReader
fromString: responseObject` all the object three is converted to a
Dictionary, and what I want is to be able to:

1. Determine whether there was an error in the response
2. If there was no error, convert the 'result' field to my preferred
class of object instead of a Dictionary. I plan to make my classes
inherit from NeoJSONObject though.

All the above to avoid the use of an intermediate set of nested
dictionaries (which could be in the thousands).
I understand I could subclass NeoJSONReader to perform that at the
character stream level, but I wanted to ask first whether there is a
pattern/configuration of dealing with something like this.

Best regards!

[1] http://www.jsonrpc.org/specification#response_object

Esteban A. Maringolo

Esteban,

I had a quick look at the spec you mentioned.

I am a bit puzzled though. Result can be anything, so how are you going to map that to specific classes (and why) ? That would require serious prior knowledge and even then, not every situation can be mapped easily to a class.

You speak about subclassing NeoJSONObject, which is cool, because it is so flexible, but then why type it further ?

If I were you, I would at least start the easy/lazy way. For example you could do

  NeoJSONObject fromString: '...'

And see how far you get. If things get slow, I would look for alternatives.

Sven

2017-07-26 18:36 GMT-03:00 Sven Van Caekenberghe <[hidden email]>:
> Esteban,
>
> I had a quick look at the spec you mentioned.
>
> I am a bit puzzled though. Result can be anything, so how are you going to map that to specific classes (and why) ?
> That would require serious prior knowledge and even then, not every situation can be mapped easily to a class

Since I'm going to use it in the context of RPC calls, I can know
beforehand what kind of class is the result, so I want to leverage
that knowledge to avoid going through an intermediate Dictionary/map
to build the object.

> You speak about subclassing NeoJSONObject, which is cool, because it is so flexible, but then why type it further ?
> If I were you, I would at least start the easy/lazy way.
> For example you could do
>   NeoJSONObject fromString: '...'
> And see how far you get. If things get slow, I would look for alternatives.

Yeap... I took your advice after making things unnecessarily complex...
after the first... and second attempt.
I tried to make a client too smart and early optimize for things I
haven't used before,
so I ended up making stuff convoluted (I'm specialist).

Long story short, I almost ended up where I started, which was a fork of
LtRpcJsonClient, with some minor fixes, using NeoJSON instead of the
JSON package for parsing/writing and using NeoJSONObject as mapClass,
named: NeoJSONRPCClient [1]

I'm using it to build a particular client that uses JSON-RPC, so most
of my specific needs were moved/implemented in my still unfinished
client subclass, if behavior becomes abstract enough, I can push it up
to the "general purpose" client.

I didn't skip the build of the map object, but for my domain specific
classes I pass the map to my specific instances, so each instance
holds a reference to the map object used to build it. I didn't feel
comfortable subclassing domain specific classes from Dictionary.

Regards!

Esteban A. Maringolo

[1] It's available at https://github.com/eMaringolo/NeoJSONRPC but I'm
still learning how to do Baselines and other stuff to work with this
pet-project I'm using to learn Iceberg. So the baseline doesn't
work... yet :|