mirror of
https://github.com/Jermolene/TiddlyWiki5
synced 2024-10-30 06:36:17 +00:00
80 lines
3.9 KiB
Plaintext
80 lines
3.9 KiB
Plaintext
caption: Macro Definitions
|
|
created: 20150220181617000
|
|
modified: 20180820165115455
|
|
tags: WikiText
|
|
title: Macro Definitions in WikiText
|
|
type: text/vnd.tiddlywiki
|
|
|
|
A [[macro|Macros]] is defined using a `\define` [[pragma|Pragma]]. Like any pragma, this can only appear at the start of a tiddler.
|
|
|
|
The first line of the definition specifies the macro name and any parameters. Each parameter has a name and, optionally, a default value that is used if no value is supplied on a particular call to the macro. The lines that follow contain the text of the macro text (i.e. the snippet represented by the macro name), until `\end` appears on a line by itself:
|
|
|
|
<$codeblock code={{$:/editions/tw5.com/macro-examples/say-hi}}/>
|
|
|
|
Alternatively, the entire definition can be presented on a single line without an `\end` marker:
|
|
|
|
```
|
|
\define sayhi(name:"Bugs Bunny") Hi, I'm $name$.
|
|
```
|
|
|
|
A more formal [[presentation|Macro Definition Syntax]] of this syntax is also available.
|
|
|
|
!! Accessing variables and parameters
|
|
|
|
Inside the macro there are several methods for accessing variables defined outside of the macro or parameters from the macro parameter list.
|
|
|
|
|syntax|description|h
|
|
|`$...$`|Text substitution of a parameter defined in the macro parameters list |
|
|
|`<<__...__>>`|Parameter-as-variable access to a parameter defined in the macro parameters list |
|
|
|`$(...)$`|Text substitution of a variable defined outside of the macro |
|
|
|`<<...>>`|Access to a variable (or other macro) defined outside of the macro |
|
|
<br>
|
|
|
|
!!! Placeholders `$(...)$`
|
|
|
|
The macro can contain placeholders for parameters. These consist of a parameter name between dollar signs, like `$this$`.
|
|
|
|
The macro can also contain placeholders for [[variables|Variables]]. These consist of a variable name (or macro name) between dollar signs and round brackets, like `$(this)$`.
|
|
|
|
The actual value of the parameter or variable is substituted for the placeholder whenever the macro is called:
|
|
|
|
<$importvariables filter="$:/editions/tw5.com/macro-examples/say-hi-using-variables">
|
|
<$codeblock code={{$:/editions/tw5.com/macro-examples/say-hi-using-variables}}/>
|
|
<$macrocall $name=".example" n="1"
|
|
eg="""<$set name="address" value="Rabbit Hole Hill">
|
|
<<say-hi-using-variables>>
|
|
</$set>"""/>
|
|
</$importvariables>
|
|
|
|
!!! Parameters as Variables `<<__...__>>`
|
|
|
|
Parameters in a wikitext macro can be accessed as variables by using the syntax `<<__...__>>`, i.e the parameter name surrounded by double underscores. For example, the example above could also be expressed as:
|
|
|
|
```
|
|
\define sayhi(name:"Bugs Bunny") Hi, I'm <$text text=<<__name__>>/>.
|
|
```
|
|
|
|
Accessing parameters as variables only works in macros that are wikified and not, for example, when a macro is used as an attribute value. The advantage of the technique is that it avoids the parameter value being substituted into the macro as a literal string, which in turn can help avoid issues with parameters that contain quotes.
|
|
|
|
For example, consider this macro. It invokes another macro using the single parameter as an argument for it:
|
|
|
|
```
|
|
\define film-quote(line) <$macrocall $name="anothermacro" actor="Bugs Bunny" line="""$line$"""/>
|
|
```
|
|
|
|
The code above will fail if the macro is invoked with the argument containing triple double quotes (for example `<<film-quote 'I quote thrice """ - see!?'>>`). Using parameter variables offers a workaround:
|
|
|
|
```
|
|
\define film-quote(line) <$macrocall $name="anothermacro" actor="Bugs Bunny" line=<<__line__>>/>
|
|
```
|
|
|
|
!! Scope
|
|
|
|
Macros are available to the tiddler that defines them, plus any tiddlers that it transcludes.
|
|
|
|
To make a macro available to all tiddlers, define it in a tiddler that has the tag <<.tag $:/tags/Macro>>.
|
|
|
|
It is also possible to write a macro as a [[JavaScript module|https://tiddlywiki.com/dev/index.html#JavaScript%20Macros]]. ~JavaScript macros are available to all tiddlers, and offer the maximum flexibility.
|
|
|
|
A tiddler can manually import macro definitions from a [[selection|Title Selection]] of other tiddlers by using the <<.wlink ImportVariablesWidget>> widget.
|