This makes tiddler A display its title with a yellow background (see [[Styles and Classes in WikiText]] to learn about CSS style). Imagine that you want to display the title in the same way in tiddler B. But you don't want to copy/paste the style instructions, because you might want to change the background colour later and you want to keep it consistent among tiddlers. This looks like a typical case of transclusion, so let's try to transclude tiddler A in tiddler B the usual way with ``{{A}}``. You should see the following content in tiddler B:
<<<
@@background-color:yellow;
Hello, my title is A
@@
<<<
The style is applied as expected, but the title is wrong: we want ``{{!!title}}`` to refer to the target tiddler B, and not the source tiddler A.
The solution is to use a \\template\\. In this case, the source tiddler A is called the [[TemplateTiddler|TemplateTiddlers]], and it is //applied// to tiddler B using the notation ``{{||A}}``. The difference is that any TextReference which does not refer explicitly to a specific tiddler is applied to the [[current tiddler|CurrentTiddler]], that is, the target tiddler. As a result, tiddler B now looks as expected:
Transcluding via a template is like applying a mask: assuming that the source tiddler contains generic references (like eye holes in a mask), these will be replaced with the target tiddlers values (like the eyes of the person who wears the mask).
A template can be applied to any tiddler, not necessarily the current one. This is achieved using the full notation ``{{<target>||<template>}}``. The default ``<target>`` is the [[current tiddler|CurrentTiddler]] (this is what we used in the above example).
! Examples
!! A predefined template to render tags nicely
You can apply the system template ``$:/core/ui/TagTemplate`` to a tag in order to see it as a tag pill with a drop-down menu:
```
{{Transclusion||$:/core/ui/TagTemplate}}
```
is rendered as {{Transclusion||$:/core/ui/TagTemplate}}
