mirror of
https://github.com/Jermolene/TiddlyWiki5
synced 2024-12-25 01:20:30 +00:00
98af893443
Thanks @kookma (see https://github.com/Jermolene/TiddlyWiki5/pull/6666#issuecomment-1514860999)
79 lines
3.2 KiB
Plaintext
79 lines
3.2 KiB
Plaintext
created: 20220917154902906
|
|
modified: 20230419103154328
|
|
tags: WikiText Macros
|
|
title: Macro Parameter Handling
|
|
type: text/vnd.tiddlywiki
|
|
|
|
!! Introduction
|
|
|
|
[[Macros]] parameters are handled in two different ways:
|
|
|
|
# Textual substitution is always performed for each parameter before the macro contents is used
|
|
# When the macro contents are wikified the parameters are made available as variables. The variable names are formed by wrapping the parameter name with double underscores
|
|
|
|
Somewhat confusingly, in some situations both of these mechanisms will occur; this is related to the [[pitfalls of using macros|Macro Pitfalls]].
|
|
|
|
!! Textual Substitution of Parameters and variables
|
|
|
|
The following substitutions take place before the text of a macro is used:
|
|
|
|
* The pattern `$param$` is replaced with the value of the named parameter
|
|
* The pattern `$(variable)$` is replaced with the value of the named variable
|
|
|
|
The actual value of the parameter or variable is substituted for the placeholder whenever the macro is called:
|
|
|
|
<$macrocall $name="wikitext-example-without-html" src="""\define say-hi-using-parameters(name,address)
|
|
Hi, I'm $name$ and I live in $address$.
|
|
\end
|
|
|
|
<<say-hi-using-parameters name:"Bugs" address:"Rabbit Hole Hill">>
|
|
"""/>
|
|
|
|
Here's an example using variable substitution:
|
|
|
|
<$macrocall $name="wikitext-example-without-html" src="""\define say-hi-using-variables()
|
|
Hi, I'm $(name)$ and I live in $(address)$.
|
|
\end
|
|
|
|
\define name() Bugs
|
|
|
|
<$let address="Rabbit Hole Hill">
|
|
<<say-hi-using-variables>>
|
|
</$let>
|
|
"""/>
|
|
|
|
<<.warning """It is important to note that if the text being inserted contains any substitution tokens then they will in turn be processed. This can lead to unexpected results.""">>
|
|
|
|
!! Accessing Parameters as Variables
|
|
|
|
When macros are wikified, the parameters can be accessed as variables with the name of the parameter wrapped with double underscores. For example, the parameter `address` would be accessed as the variable `__address__`.
|
|
|
|
Thus, the example above could also be expressed as:
|
|
|
|
<$macrocall $name="wikitext-example-without-html" src="""\define say-hi-using-parameters(name,address)
|
|
Hi, I'm <<__name__>> and I live in <<__address__>>.
|
|
\end
|
|
|
|
<<say-hi-using-parameters name:"Bugs" address:"Rabbit Hole Hill">>
|
|
"""/>
|
|
|
|
Accessing parameters as variables only works in macros that are wikified and not, for example, when a macro is used as an attribute value.
|
|
|
|
!!! Advantages of Accessing Parameters as Variables
|
|
|
|
The primary advantage of the technique is that it avoids the parameter value being substituted into the macro as a literal string, which in turn can help avoid issues with parameters that contain quotes.
|
|
|
|
For example, consider this macro. It invokes another macro using the single parameter as an argument for it:
|
|
|
|
```
|
|
\define film-quote(line) <$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__>>/>
|
|
```
|
|
|
|
See [[Macro Pitfalls]] for more discussion.
|