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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