Setting the emptyValue in Set Widget

[Mohammad]

I have a small macro to sweep a list of tiddlers from first to last

Here parent is a tag name some tiddlers has been tagged with. The following code works

Here I have used two set widgets, one to set the emptyValue

\define nextItem(parent)

 <$set 

   filter='[tag[$parent$]first[]]'

   name=emptyTid

  >

 <$set

 filter='[tag[$parent$]after{!!temp}]'

 name=NewIndex

 emptyValue=<<emptyTid>>

 >

  <$action-setfield

   $tiddler={{!!title}}

   temp=<<NewIndex>>

   />

</$set>

</$set>

\end

<$button actions=<<nextItem "myTag">> >Next</$button>

But if I directly set the emptyValue and I have used only one set widget. But it does not work!!

\define nextItem(parent)

 <$set

 filter='[tag[$parent$]after{!!temp}]'

 name=NewIndex

 emptyValue='[tag[$parent$]first[]]'

 >

  <$action-setfield

   $tiddler={{!!title}}

   temp=<<NewIndex>>

   />

</$set>

\end

<$button actions=<<nextItem "myTag">> >Next</$button>

What is the problem? Why I have to use two set widegets?

/Mohammad

[Jeremy Ruston]

Hi Mohammad

But if I directly set the emptyValue and I have used only one set widget. But it does not work!!

\define nextItem(parent)

 <$set

 filter='[tag[$parent$]after{!!temp}]'

 name=NewIndex

 emptyValue='[tag[$parent$]first[]]'

 >

  <$action-setfield

   $tiddler={{!!title}}

   temp=<<NewIndex>>

   />

</$set>

\end

<$button actions=<<nextItem "myTag">> >Next</$button>

What is the problem? Why I have to use two set widegets?

The problem here is that the emptyValue attribute of the set widget is interpreted as a string, not as a filter. So, rather than getting the results of the filter you'll get the text of the filter itself.

Things should work if you add the triple braces filtered transcluded attribute syntax:

\define nextItem(parent)

 <$set

 filter='[tag[$parent$]after{!!temp}]'

 name=NewIndex

 emptyValue={{{ [tag[$parent$]first[]] }}}

 >

  <$action-setfield

   $tiddler={{!!title}}

   temp=<<NewIndex>>

   />

</$set>

\end

<$button actions=<<nextItem "myTag">> >Next</$button>

The triple braces syntax can be used with any attribute: the attribute is assigned the first result from evaluating the filter.

Best wishes

Jeremy.

/Mohammad

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[Mohammad]

Wonderful!

Jeremy is there any document in tiddlywiki.com or other placed to explain these rules?

Examples like:

{!!title}
{!!title}
<myVar>
<<myVar>>

Best

Mohammad

[Jeremy Ruston]

Hi Mohammad

On 29 Jun 2018, at 08:33, Mohammad <mohammad...@gmail.com> wrote:

Jeremy is there any document in tiddlywiki.com or other placed to explain these rules?

There is an attempt to document this stuff at https://tiddlywiki.com/#Transclusion%20and%20Substitution

Best wishes

Jeremy.

[Mohammad]

Thank you Jeremy!

Best wishes

Mohammad

[Mohammad]

Jeremy,

 One more point:

When the result of filter in the set widget is tiddlers with space in the name like My Tiddler, the list widget return [[My Tiddler]] this cause the code breaks. Note to [[]] in the result.

Based on your explanation I used the following syntax

\define nextItem(parent)

<$set

 filter={{{ [tag[$parent$]after{!!temp}]}}}

name=NewIndex

emptyValue='[tag[$parent$]first[]]'

>

 <$action-setfield

  $tiddler={{!!title}}

  temp=<<NewIndex>>

  />

</$set>

\end

No it works! I mean the new code works even when the filter return [[My Tiddler]]?

Is it the correct way?

/Mohammad