Bob,
My first observation from your post is the filter contains;
- id*{[<<__*name_id__*>>]*is[blank]then[XX]*}sort[title]]}*
Which seems to include multiple syntax issues.
Something that took me years to learn which may help if you is;
In wiki text we can also use html which uses <htmltag></htmltag> so to
allow macros we use <<macroname>> and for widgets we use <$widgetname> for
transclusion we use {{ tiddlername }}
When you use a filter, where html is not possible, you do not need to
differentiate between <htmltag> and <<macroname>>, in fact both are illegal
in filters, etc.. so we remove a layer of brackets
The following is appropriate in a filter
- <varname> (not you can use <macroname> but not <macroname params> in
filters
- {tiddlername} returns content in tiddlername
- {!!fieldname} returns content in currenttiddlers fieldname
- Because a set of brackets already delimits a varname Rather than
operator[<varname>] we use operator<varname>
- Keep in mind we can use substitutions in filters $param$ and
$(varname)$ $(*Not retested recently by me*)$ however (substitutions
need not contain delimiters) so we use operator[$varname$]
A Quick note is that <<__...__>>
see https://tiddlywiki.com/#Macro%20Definitions%20in%20WikiText
<<__...__>> Parameter-as-variable access to a parameter defined in the
macro parameters list
There are a few cases where using a parameter named in the \define pragma,
normally in the form $parameter$, is not what you need
- which simply substitutes $parameter$ with the value in the parameter,
eg text="$parameter$"
This Parameter-as-variable method simply lets you pass that parameter as if
it were a variable
- eg text=<<__parameter__>> There are a FEW cases where this was
essential.
however I tend to find more value using the substitution forms in macros
because there is less need to concatenate values
- eg; tooltip="This is the $tooltipparam$ works"
- And access a variable and use as substituton $(varname)$ (only in
macro definitions)
The exception to this is demonstrated in this example where I imediatly
convers parameters into variables to allow defaults to be computed.
\define macroname(input-parm)
<$set name=input-parm value="$input-parm$" emptyValue=<<othermacrofordefault
>> >
Use input-parm=<<input-parm>> as a result I will not use the original
$input-parm$ or the original <<__input-parm__>> in here
</$set>
\end
This method allows for more sophisticated or computed default values, and
relies on emptyValue or in $list emptyMessage
So I do not mislead you another way to handle defaults for parameters that
are *literal strings* is as follows
\define macroname(input-parm:"defaultstring")
Use the original $input-parm$ or the original <<__input-parm__>> in here
\end
Regards
Tones
On Wednesday, 16 September 2020 08:00:33 UTC+10, Dr Bob Jansen wrote:
>
> Eric,
>
> Thanks for your reply.
>
> One question. You reference the macro parameter using multiple braces but
> the documentation says to use <<__...__>>. Is this documented somewhere?
>
> BobJ
>
> ---------------
>
> Dr Bob Jansen
>
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> On 16 Sep 2020, at 01:30, Eric Shulman <[email protected] <javascript:>>
> wrote:
>
> On Tuesday, September 15, 2020 at 5:44:56 AM UTC-7, Bob Jansen wrote:
>>
>> How can I check if a parameter passed to a macro is blank?
>> I have tried
>> \define purchased(name_id)
>> <$list
>> filter="[tag[Artworks]!tag[Index]!<currentTiddler>search:name_id{[<<__name_id__>>]is[blank]then[XX]}sort[title]]}>•
>>
>> <$link to={{!!artwork_id}}><$view field="title"/> <$view
>> field="artwork_title"/></$link><br/></$list>
>> \end
>> but this does not work. If name_id is empty I want to search to look for
>> the string XX which I know doesn't exist.
>>
>
> First, as you may have realized, the above doesn't work because you can't
> "nest" filter syntax (i.e., you can't directly use a filter to describe
> another filter's operand value)
>
> To accomplish your goal, first calculate the desired operand value and
> assign it to a variable. Then reference the variable in the filter, like
> this:
> \define purchased(name_id)
> <$vars id={{{ [[$name_id$]!is[blank]else[XX]] }}}>
> <$list filter=
> "[tag[Artworks]!tag[Index]!match<currentTiddler>search:name_id<id>]">
> • <$link to={{!!artwork_id}}><$view field="title"> <$view field=
> "artwork_title"/></$link><br/>
> <$list>
> </$vars>
> \end
>
> Alternatively, since you know that searching for [XX] will result in no
> matching tiddlers, you could test for the blank value and just skip the
> $list entirely:
> \define purchased(name_id)
> <$list filter="[[$name_id$]!is[blank]]" variable="not_blank">
> <$list filter=
> "[tag[Artworks]!tag[Index]!match<currentTiddler>search:name_id[$name_id$]]"
> >
> • <$link to={{!!artwork_id}}><$view field="title"> <$view field
> ="artwork_title"/></$link><br/>
> <$list>
> </$list>
> \end
> The outer filter is being used as a conditional ("if name_id is not
> blank") with the variable ("not_blank") used to avoid changing the value of
> <<currentTiddler>>.
> Note: I like to use a variable name that summarizes the purpose of the
> filter, but you could use any variable name (e.g., "foo") since you really
> don't reference it anywhere.
>
> -e
>
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