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Improvements to wording

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Astrid Elocson 2014-12-28 09:51:53 +00:00
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tags: Concepts
title: DataTiddlers
Data tiddlers provide a way to access blocks of [[JSON]] data within the `text` field of a tiddler.
A data tiddler is a miniature database contained within a tiddler.
//The implementation of data tiddlers is preliminary, with some intentional limitations.//
There are two standard formats:
! Data tiddler format
* DictionaryTiddlers
* [[JSONTiddlers]]
A native data tiddler must have:
Other formats of tiddler can also be parsed to yield blocks of data that behave like data tiddlers.
* The ContentType field `type` set to `application/json`
* Valid JSON data in the `text` field
For example, the [[history list|$:/HistoryList]] tiddler is a data tiddler.
Other tiddler types with alternative formats can also be parsed to yield a block of data that behaves like a data tiddler.
!! Tiddler dictionary format
The tiddler dictionary format is an alternative syntax for data tiddlers:
* The ContentType field `type` is set to `application/x-tiddler-dictionary`
* The `text` field consists of one or more lines of the form `<name>:<value>`
For example, palettes such as the [[default Vanilla palette|$:/palettes/Vanilla]] are tiddler dictionaries.
! Accessing data within data tiddlers
Currently, it is only possible to access the top level properties of the data using TextReference syntax.
For example, given a `application/json` tiddler containing:
Use a TextReference to look up a value by its name. For example, if a [[DictionaryTiddler|DictionaryTiddlers]] called `MonthDays` contains:
```
{"a":"one","b":"two","c":"three"}
oct:31
nov:30
dec:31
```
Or the equivalent tiddler dictionary of type `application/x-tiddler-dictionary`:
... then `{{MonthDays##nov}}` will resolve to the value `30`.
The same is true if `MonthDays` is a [[JSONTiddler|JSONTiddlers]] with the following content:
```
a:one
b:two
c:three
{"oct":31,"nov":30,"dec":31}
```
With either of those definitions `{{TiddlerTitle##b}}` would have the value `two`.
Note: //It is currently only possible to retrieve data from the immediate properties of the root object of a JSONTiddler.//