Hi Joshua,
thanks so much for your answer. This has taken me a lot further.
But, reconsidering my original question, I found, that, maybe, I got stuck
too much in the procedural paradigm, and a more elegant approach would be,
if one could could use each[] for looping through a JSON array. Taking your
example this should look something like:
<$list filter="[[MyJson]indexes[/path/to/array]each[]]">
{{##FieldFromJsonArray}}
</$list>
I tried to do it, but didn't succeed. I understand that each[] expects a
list separated with spaces, so my assumption would be that this does not
work unless an overloaded version of each[] is provided. OTOH, I found an
undocumented function ForEach[] in JSONMANGLER. Any clue?
I created three JSON test tiddlers. One with a nested array of 4 elements
and another with 3 and a third one with a one-element array. I looped
through them like this
<$list filter="[tag[Facility]]">
...
<$set name="arrLength" filter="[indexes[/Actions]count[]]">
Array Length: <<arrLength>>
</$set>
</$list>
and was able to display all fields and the array fields as JSON text.
Strangely, the arrLength variable displayed a value of 4 for all three
tiddlers. No idea why. Will have to dive deeper into it.
Thanks again
Werner
Am Samstag, 11. Juli 2020 21:24:07 UTC+2 schrieb Joshua Fontany:
>
> Hi,
>
> Great to see people experimenting with my tools.
>
> Two things to note. 1) 0-index based arrays can always have a new object
> written to an index equal to the length of the array. Example, "[0,1,2]", I
> can push "3" to {{MyJson##3}}, and it will be "[0,1,2,3]". Neat trick. 2)
> You can count an array's length using filters as long as you know the
> position of the array within the nexted JSON structure, like so:
> ```
> <$var name="arrLength" filter="[[MyJson]indexes[/path/to/array]count[]]">
> Array Length: <<arrLength>>
> </$var>
> ```
>
> Combine the two techniques like so (note the final slash on the new path
> gets added on as a prefix before adding the path to the array):
> ```
> <$var name="arrLength" filter="[[MyJson]indexes[/path/to/array]count[]]">
> <$var name="newIndex"
> filter="[<arrLength>addprefix[/]addprefix[/path/to/array]]">
> <$button setTitle="MyJson" setIndex=<<newIndex>> setTo="New Data" />
> </$var>
> </$var>
> ```
> You could use the form `setTo={{New Data Tiddler}}` to grab the new data
> from the text-field of the "New Data Tiddler", etc, etc.
>
> Best,
> Joshua Fontany
> On Friday, July 10, 2020 at 1:14:52 AM UTC-7 Werner wrote:
>
>> Hi Tony,
>>
>> thanks for taking your time and your extensive reply. Perhaps I've made
>> it too complicated. Ok, I try to reformulate it. Disclaimer also: I work in
>> a corporate environment, so I'm not completely free in the tools I am
>> allowed to use (to my surprise, Node.js is ok - yessss!) and how much
>> information I can disclose.
>>
>> Let's put it that way: I have set up an internal information repository
>> which contains more or less textual information only so far. But now and
>> then, I would like to display some figures. And I would have to perform
>> some simple arithmetics with that figures (basically summing up).
>>
>> Let's call the things I am looking at "facilities". A "facility" should
>> be displayed in a templated tiddler, displaying textual and quantitative
>> information. Each "facility" can feature several "units" (that's the 1:n
>> relation), figures for which should also be displayed and/or shown as a
>> grand total.
>>
>> The data for the facility/unit information should initially come from an
>> Excel table. For further use (the CRUD part), I would like to create a
>> TW-based interface. As "facility" is a comprehensive entity for my
>> purposes, I thought it would be ok to store it in a nested JSON tiddler,
>> i.e. store the units per facility in a JSON array. This, of course, breaks
>> the RDBMS dogma, but it saves me from having to fiddle with primary keys.
>> Mimicking a RDBMS in TW is definitely not a rabbit hole I want to jump
>> into. If I needed something like that, I would try if I could connect a DB
>> backend via Node.js (in my special environment I would end up with SQLite
>> or ODBC), and let this do the grunt work.
>>
>> All this being said, here's the core of my question: Accessing nested
>> JSON data using Joshua Fontenay's JSONMANGLER plugin works great, as long
>> as the index position is known, but I need a way to determine the length of
>> a variable-length array in a JSON structure, for not running out-of-bounds
>> while looping into the nested data. I understand $:/History is such a
>> variable-length array, and thanks for pointing me at this. In that case,
>> maybe I need to look up how data are retrieved from there. I know, as a
>> workaround, I still could store the number of units as a data field in the
>> JSON structure, but then I would have to take care of it programatically,
>> which I want to avoid.
>>
>> Thanks again and apologies for any confusion I caused
>> Werner
>>
>>
>> TW Tones schrieb am Freitag, 10. Juli 2020 um 01:19:01 UTC+2:
>>
>>> Werner,
>>>
>>> Despite clearly having a lot in common with an understanding of
>>> databases I don't completely follow you need or argument here. However I
>>> believe I can offer you some helpful leads.
>>>
>>> One part that confuses me is your 1:n or one to many, I have already
>>> build one to one, one to many and many to many half a dozen ways without a
>>> data tiddler in tiddlywiki. What is the particular issue here?
>>>
>>> First look at tiddlywikis existing functionality.
>>>
>>> - The history mechanism stores tiddler titles and more during a
>>> session in the $:/historyList this may be an analogue
>>> - The Import and export mechanism extract and package tiddlers as
>>> json representations
>>> - Mohammad's Trash Plugin moves deleted tiddlers into another
>>> structure to keep them aside, I think it is JSON as well.
>>> - In my demo site here
>>> <https://anthonymuscio.github.io/ActiveTiddler.html> the active
>>> tiddler process extracts titles from the history list using splitregexp
>>> not
>>> standard JSON as the key is not unique
>>>
>>> However It would not necessarily be too concerned about using tiddlers
>>> unless your number will be truly astounding in numbers. We had a 66,000
>>> word tiddler example in the last year and that was single file.
>>>
>>> Speculation
>>>
>>> If you packed more static tiddlers (eg a reference table) into a plugin
>>> and access them as shadow tiddlers you are effectively packing them into a
>>> json file and allow yourself to edit exceptions and the database becomes
>>> the combination of the packaged and overwritten providing a lot of
>>> flexibility to your design. In effect you CRUD will make use of standard
>>> tiddlywiki features, just treat the records like standard tiddlers. The D
>>> or delete of CRUD could get smart (adding and removing from JSON) or you
>>> could simply flag deleted tiddlers as such and treat them as deleted with
>>> an occasional rebuild recommended after N tiddlers are flagged as deleted.
>>>
>>> I can already foresee a lot of sophisticated features being possible
>>> including tracing and logs, difference engines, database snapshot at a
>>> point in time and more. I have recently designed an alternative to shadow
>>> tiddlers I call ghost tiddlers that may also be a useful algorithm.
>>>
>>> Offer
>>> I as a tiddlywiki superuser, I am investing totally in the TiddlyWiki
>>> platform, if you are interested in collaboration to build a database model
>>> process, making full use tiddlywiki's unique features I think it will be a
>>> good investment in the future.
>>>
>>> Lets start the conversation.
>>>
>>> Regards
>>> Tony
>>>
>>>
>>>
>>>
>>> On Friday, July 10, 2020 at 5:38:31 AM UTC+10, Werner wrote:
>>>>
>>>> Dear all, heavy user and rare poster here. Using TW has become a daily
>>>> treat for me, but I have managed to still stay at the surface so far. Now,
>>>> I have to dive in deeper.
>>>>
>>>> I have been using TW so far to store semi-structured information, but
>>>> now I need to integrate structured information, i.e. a database featuring
>>>> an 1:n relation.
>>>>
>>>> I thought it might be a good idea using JSON. I also thought, for my
>>>> purposes, I don't want to mimic an RDBMS in TW with all the primary key
>>>> hassles and a deluge of .TID files (I am running TW on Node.js), so I
>>>> wanted to use a JSON tiddler for the entities and use arrays in JSON for
>>>> sub-entities.
>>>>
>>>> I came across Joshua Fontenay's JSONMangler plugin (Kudos, Josh!) and
>>>> so far so good.
>>>>
>>>> BUT
>>>>
>>>> Eventually I want to implement CRUD (create-retrieve-update-delete)
>>>> functionalities for this special data. And I want to display the 1:n
>>>> relation in a single tiddler. And this is where I'm stuck at the moment:
>>>>
>>>> - how to get the total number of array items in a JSON array in order
>>>> to be able to display the 1:n
>>>>
>>>> apart from the variable array length, the JSON structure is fix, so
>>>> everything else should be fairly straightforward. OK, there are some
>>>> numeric fields in the array I need to sum up, but one thing after the
>>>> other...
>>>>
>>>> Any insight would be greatly appreciated
>>>>
>>>> Best,
>>>> Werner
>>>>
>>>>
>>>>
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