Re: Parsing JSON data into a data structure without knowing variable's names

Hi everybody

Thank you all for this interesting thread. Just let me sum up all I read in
it.

I would leave Javascript outside this discussion, because I have to do this
job in pure RPG ILE without the help of WDSC or other develop environment.
Anyway, JSON format being pretty much similar to Javascript object
description is done on purpose as it makes data immediately available in a
Javascript object just after being read.

I think all of you got the point of my request, which is to programmatic
read JSON data to be loaded into a data structure; anyway, from all your
answers it seems impossible to match a JSON pair name/value with a DS
variable/value and that leads to build a couple of programs: a generator
code which knowing the data structure to be loaded can write appropriate
specifications which in turn know what to read.

Because the obstacle here is how to make a JSON node identifying itself in
a given data structure, as Jon clearly pointed out.

In my case, types and lengths of variables against those of JSON values are
not an issue, because they must match otherwise an error should arise.

Let me try to reverse the approach: my routine starts looping through the
data structure definition, let's say by reading DS D specifications or
whatever is needed as this is a different topic, then the generic routine
can look for a specific information into the JSON. But how? Given my
ignorance, I guess variables' names are converted into pointers at compile
time, but is there a way to reverse the process so that to obtain a
variable which contains the name of a variable given a pointer?


2017-08-14 3:55 GMT+02:00 Jon Paris <jon.paris@xxxxxxxxxxxxxx>:

You missed my point Brad - which was that YAJL_OBJECT_LOOP will loop
through anything. The rest of it was just showing how the generic object
can be compared to find its identity.

But I agree in as much as one always needs to know something in a business
processing environment. Unless you are simply writing a utility to report
(for example) on what it finds.


Jon Paris

www.partner400.com
www.SystemiDeveloper.com

On Aug 13, 2017, at 12:22 PM, Bradley Stone <bvstone@xxxxxxxxx> wrote:

On Sun, Aug 13, 2017 at 1:53 PM, Jon Paris <jon.paris@xxxxxxxxxxxxxx>

wrote:

Not necessary to know the structure Nathan as you can query what kind

of node you are dealing with.

A straight object loop can also be used - for example:

Dow YAJL_OBJECT_LOOP( customerNode: i: key: node );
Select;
When key = 'ID';
customer(c).id = YAJL_GET_NUMBER( node );
When key = 'Name';
customer(c).name = YAJL_GET_STRING( node );

In this instance I only need certain fields and the names are known -

but the YAJL_OBJECT_LOOP itself dd not require that I know the names or
types of the objects.

How is knowing the names, data types and container not knowing the

structure?

You know you're in a customer array that contains at least a numeric
ID and character name. I'd say that's at least knowing the structure
at least partially, if not wholly.

As I said earlier I think code gen is the way to go - but the JSON

structure can be dynamically determined just as XML-SAX allows you to do
with XML.

Yes, that makes sense, but once you do the program "knows" the
structure and is built appropriately around thus said structure.

Bradley V. Stone
www.bvstools.com
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