The Mystery of SetWidget

#1

Set widget (i.e. $set) is a very powerful widget which is not known to many users (or underestimated its power)! In this post some of interesting use cases of set widget are discussed.

Example one

I want to do ThisJob if a condition meets and OtherJob if a condition doesn’t meet

<$set name=Job 
            filter="check-some-conditions" 
            value=ThisJob 
            emptyValue=OtherJob>
   <$macrocall $name=<<Job>> />
</$set>

for illustration

\define  ThisJob() With Tiddlywiki we are on the moon
\define  OtherJob() Oh no, without Tiddlywiki, life is too hard for us!

<$set name=Job 
      filter="[tag[hirad]count[]compare:integer:gteq[4]]" 
      value=ThisJob 
      emptyValue=OtherJob>
   <$macrocall $name=<<Job>> />
</$set>

The condition tells [tag[hirad]count[]compare:integer:gteq[4]] if there are 4 or more tiddlers tagged with hirad do ThisJob otherwise do OtherJob.

Instead of macros, one can use transcluded tiddlers, etc.

Note: This is a wiki post, everybody is welcome to edit and add his/her contents directly here

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#2

Another feature of the set widget is using it as a cascade;

<$set name=variablename value="$param$" emptyValue=<<othervarname>> >
<$set name=variablename value=<<variablename>> emptyValue={{!!fieldname}} >
<$set name=variablename value=<<variablename>> emptyValue={{tiddlername}} >
<$set name=variablename value=<<variablename>> emptyValue="default" >

In here the value of <<variablename>>  will be set to the first value found.
$param$ or <<othervarname>> or {{!!fieldname}} > or {{tiddlername}} or default.

</$set></$set></$set></$set>

Although these may suffice if you only need the final result.

<$set name=variablename filter="[[$param$]] ~[<othername>] ~[{!!fieldname}] ~[{tiddlername}] ~[[default]]">
or 
<$set name=variablename filter="[[$param$]] [<othername>] [{!!fieldname}] [{tiddlername}] [[default]] +[first[]]">

Above not tested today.

2 Likes
#3

This magic is possible in TiddlyWiki 5.3.2 using conditionals (e.g. <%if ...condition %>).