Passing a filter to a macro, when the filter includes replaceable parameters

1

Passing a filter to a macro, when the filter includes replaceable parameters

  • I would like to be able to pass filters to macros that make reference other replicable parameters in the macro. eg

Please consider the following macro

\define fieldname-value-select-macro(fieldname filter)
<$select field="$fieldname$"> default={{!!$fieldname$}}>
<$list filter='[all[shadows+tiddlers]each[$fieldname$]get[$fieldname$]sort[]]'>
<option value=<<currentTiddler>>><$view field='title'/></option>
</$list>
</$select>
\end

<<fieldname-value-select-macro caption>>
  • This works on tiddlywiki.com
  • Here you can set the caption on the current tiddler to any of the existing caption values (unlikely use)
  • Note how the select widget uses the filter below
    • [all[shadows+tiddlers]each[$fieldname$]get[$fieldname$]sort[]]
    • This filter obtains all the existing values from $fieldname$

What does not work

  • If I was to pass the filter above in a parameter to the macro, the macro would look like this
    • <<fieldname-value-select-macro caption "[all[shadows+tiddlers]each[$fieldname$]get[$fieldname$]sort[]]">>
  • This does not work because the filter parameter includes $fieldname$ which is not replaced by the value in the macro parameter fieldname (in this case caption)
    • if I used filter="$filter$" in the selects list widget.

Desired result

  • To make the above work out of the box, no doubt if even possible requiring a core change
    • The $filter$ would need to be expanded, then the $fieldname$ within that expanded before passing to the list widget.
    • Arguably any parameter would need to be expanded until if does not contain any other $param$
  • A smart workaround to achieve the same result
    • I believe if I set variables I can pass a filter that will be interpreted correctly (untested today) eg
      • [all[shadows+tiddlers]each<fieldname>get<fieldname>sort[]] but what chance is there we can use the suggested approach?

Thanks in advance for your considered response

2

Hi @TW_Tones, this worked for me on tiddlywiki.com:

\define fieldname-value-select-macro(fieldname filter)
<$select field="$fieldname$"> default={{!!$fieldname$}}>
<$list filter="[subfilter<__filter__>]">
<option value=<<currentTiddler>>><$view field='title'/></option>
</$list>
</$select>
\end

<<fieldname-value-select-macro caption "[all[shadows+tiddlers]each<__fieldname__>get<__fieldname__>sort[]]">>

Note the use of subfilter and the parameter-as-variable syntax, as described in https://tiddlywiki.com/#Macro%20Definitions%20in%20WikiText.

Have a nice day
Yaisog

3

Thanks, I never found a use for the <__paramname__> format until NOW!

Sweet as.

4

If I understood the developer discussions correctly, then macros using the $…$ substitution cannot be cached internally, whereas the parameter-as-variable syntax can. So, depending on how often that macro is called and how big your wiki is, this can make a difference in responsiveness of your wiki.
I believe the context of these discussion was the tag chooser and the several macros that are called for each tag in the dropdown to determine its colors. I don’t remember if it was here or on Google Groups or GitHub, though…

Personally, I try to avoid the $…$ and $(…)$ substitutions whenever possible.

Have a nice day
Yaisog

5

First thanks so much for the <__varname__> tip, this is the first compelling case I have found

Now my macro looks like this below

  • Note how the filter default is set but can be used in the macro making use of different values of the fieldname variable.
    • filter:"[all[shadows+tiddlers]each<__fieldname__>get<__fieldname__>sort[]]"
  • Now the macro calling this one, can provide an alternate filter containing <__paramname__>'s
  • All that remains is to check I am not restricted in other filter forms including field and text references and regular variables (I do not expect so as only substitution’s had this issue).
\define fieldname-value-select-macro(fieldname filter:"[all[shadows+tiddlers]each<__fieldname__>get<__fieldname__>sort[]]")
<$select field="$fieldname$"> default={{!!$fieldname$}}>
<$list filter="""[subfilter<__filter__>]""" >
<option value=<<currentTiddler>>><$view field='title'/></option>
</$list>
</$select>

Thanks for your perspective @Yaisog

FYI: I have not applied this rule and not yet come across any performance issues including in large and complex wikis.

  • This maybe because I tend to apply this to a subset of tiddlers and when in currentTiddler
  • I also write macros with parameters using $…$ and $(…)$ where they are a static string, that influences the macro by restricting the tiddlers in a list.
  • I expect if I used the filter [tag[$tagname$]] it can still leverage the tag cache.
6

That’s right.

It is possible to avoid this construction most of the times. But using it for “string” concatenation it is still very convenient and simple to use.

7

That is true, though I often use something like

{{{ [[literal string]] [<string-variable>] ... +[join[]] }}}

for that, as it is both very flexible (e.g. add space between strings) and semantic, and doesn’t need an extra \define.

Have a nice day
Yaisog

8

Yes Using filtered transclusions makes even more sense now our filters have even more operators.

  • I use the above form including with a +[join[ ]] ie contains a space especially to construct tooltips
  • However using this in a set let or var or in a “$set filter=” makes more sense if you want to use the result more than once.

A proposed changes in the works are likely to allow a new form of concatenation/replaceable/substitution unfortunately it is not clear to me which is the best link to this.