created: 201308291647
modified: 201308291647
tags: concepts
title: DataTiddlers

Data tiddlers provide a way to access blocks of [[JSON]] data within the `text` field of a tiddler.

//The implementation of data tiddlers is preliminary, with some intentional limitations.//

! Data tiddler format

A native data tiddler must have:

* 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, the [[metrics of the Vanilla theme|$:/themes/tiddlywiki/vanilla/metrics]] are a tiddler dictionary.

! 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:

```
{"a":"one","b":"two","c":"three"}
```

Or the equivalent tiddler dictionary of type `application/x-tiddler-dictionary`:

```
a:one
b:two
c:three
```

With either of those definitions `{{TiddlerTitle##b}}` would have the value `two`.