On Saturday, September 26, 2020 at 11:52:29 PM UTC-7, Bob Jansen wrote:
>
> For example, why does this not work?
> <$button>
> <$action-setfield
> $tiddler="$:/TLS/exhibition_id"
> $value={{!!exhibition_id}}
> />
> <!--append the exhibition_id to the exhibition id field in each artwork-->
> <$list filter="[tag[Mark]]">
> <$action-setfield
> $field="exhibition_id"
> $value=<<TLSconcatenate {{!!exhibition_id}}
> {{$:/TLS/exhibition_id}}>>
> />
> </$list>
>
> Link Artworks to Exhibition
> </$button>
>
> The result is the string {{!!exhibition_id}} {{$:/TLS/exhibition_id}}
> stored in the exhibition_id field of each artwork selected and not the
> transcluded values.
> TLSconcatenate is a simple macro to concatenate two strings
> \define TLSconcatenate(head tail) $head$$tail$
>
A macro does NOT "parse" anything that you pass to it. It only does TWO
things:
1) replace instances of $param$ with a value passed into the macro
2) replace instances of $(variable)$ with a value defined outside of the
macro
Macro calls (<<macroname param param ...>>) do not parse any of the
parameters before passing them into the macro.
Thus, when you use {{!!exibition_id}} and {{$:/TLS/exhibition_id}}, the
macro simply appends those two bits of syntax, unchanged.
It is up to the "calling context" to determine what happens with the result
of a macro.
If the macro occurs directly in wikitext, then the result *is* parsed and
rendered.
If the macro is used as the value of a widget parameter, it is *not* parsed.
This can lead to some confusion when trying to debug a macro:
If you invoke <<somemacro {{foo}} {{bar}}>> and display the results, the
{{foo}} and {{bar}} transclusions are parsed
and replaced with their underlying values, so it can look like the macro
does what you might be expecting.
However, if you use that same macro as a widget parameter (e.g.,
$value=<<somemacro ...>>) then the
the tranclusions are NOT processed and the macro results are just passed
along to the widget 'as-is'.
For your specific use-case (concatenating the text from two transclusions),
forget macros...
Instead, use an "inline filter" to construct the desired widget parameter
value.
"inline filters" (aka "filtered transclusion") are surrounded by
tripled-curly braces: {{{ ... }}}
and contain filter syntax, which is itself enclosed in a pair of square
brackets: [...].
Within the filter syntax, transclusions, variables, and literal text use
*single* brackets:
{...} for transclusions
<...> for variables
[...] for literal text
Thus, the $value param of your $action-setfield widget could be written
like this:
<$action-setfield
$field="exhibition_id"
$value={{{ [{!!exhibition_id}addsuffix{$:/TLS/exhibition_id}] }}}
/>
Hope this helps.
enjoy,
-e
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