How to find out if a parameter is a tag, field, or a list

#1

Hello TW-Community,

is there a way to check the type of a parameter to select the right routine for output?

I have the following situation:

I have Tiddlers with the tag Department.
AND
I have Tiddlers with fields named Department containing a name like “Human Resources”.
AND
I want to have Tiddlers with fields named Department containing a list of Departments e.g. “[[Sales Department] [Purchasing Team]]” but it is not defined how the list has to be created.

I did some tests with different procedures, but I want to have only one procedure what is doing the right output automatically.

My problem here I do not know how to select the right procedure
AND
I also have no idea what kind of definition I can use to define the list in the field and to list these items.

Here is my code so far.

code-body: yes
tags: $:/tags/Global
title: Display the right content

\whitespace trim
\procedure Display (A_Name)

\procedure show_content_of_field(content_selector)
      Field <<content_selector>> :
      <$view field=<<content_selector>><br>
\end

  \procedure show_list(list_selector)
    <$list filter='[<list_selector>]' variable="this_field">
        <$view field=<<this_field>>/><br>
    </$list>
  \end

  \procedure show_tagged_tiddlers(tag_selector)
      <$list filter='[tag<tag_selector>sort[caption]]' variable="title_of_field">
          <$view tiddler=<<title_of_field>> field="caption" /><br>
      </$list>
  \end

<!-- if A_Name is a tag then <<show_tagged_tiddlers A_Name -->
<!-- OR -->
<!--  if A_Name contains a list then <<show_list A_Name -->
<!-- OR -->
<!--  if A_Name contains not a tag and not a list then <<show_tagged_tiddlers A_Name -->

\end

I am curious about the solutions
Stefan

#2

Having the same variable-name for fundamentally different types is a bad idea. For a tag there is the is-operator, which could be used to identify if a string is used as a tag. But that does not mean that it has be read from a tag.

So if you have a filter like <$list filter ="[tag[HelloThere]]" ... the currentTiddler variable will contain the tiddler titles that are tagged HelloThere. Most of those variables are also used as tags. So <%if [<currentTiddler>is[tag]]%>could be used to identify if it is used as a tag. But it does not know if the value was created by using [tag[HelloThere]]. It could have been created with <$list filter="[list[HelloThere]]".., which is a completely different thing.

So no you can not identify, where a variable did come from The only way is to use proper variable naming.

If a field contains a single value it should be named department – in singular. I personally always start variable names and field-names with lowercase. So I do not need to think about it.

If a field contains list I would name it departments or dep-list which makes it clear that it can contain title lists. Even if the list field only conatains one value.

If you want to create a procedure that does behave differently, depending on what type of value you feed it, you will need to give it a second parameter.

(The code is not tested)

\procedure show(selector, type:"tag")
<% if [<type>match[tag]] %>
    <!--> do something --> 
<% elseif [<type>match[list]] %>
    <!--> do something --> 
<% else %>
    <!--> do something --> 
<% endif %>
/end

Hope that helps
-m

#3

What I’m currently using is a prefix for the name, this helps to differentiate.

So for example Li-department, Ta-department, and Fi-department.

You can strip these away if needed, it’s a recent topic here.

Unfortunately, it could be a bit of work, depending on the size. Tw does help a lot by showing where changes are needed, etc.

Hope this helps