How can I add and retrieve a field depending on the occurence a tag?

1

Hi dear tiddloists,

I want to achieve the following, any ideas or hints around about it? I want to start some coding to improve my tw experience.

  • triggered by the creation of a certain tag in the tiddler (i.e. let us say a tag “abbreviation”) I want to insert a field or fields (i.e. “abbreviation_resolved”) programmatically. Adding template into the text would be helpful as well.
  • It would also be nice to evaluate have existing tiddlers against a constraint definitions like, for the given example, do all abbreviation tiddlers have that field.

Is anyone aware of existing pieces I could take as a starting point(s) to achieve something pointing into that direction? On the long run, I would be interested to achieve somthing like a way or form to handle general tiddler constraint definitions.

Critical comments are welcome, if you feel the approach is wrong, please let me know!

Thanks and greetings,
Frank

2

For your first question.
You can set up a template tiddler to automatically apply a template to a specific tag.

You can either set up your template in a tiddler named ‘what ever’ and then cal it in your target tiddler with
{{||$:/what ever}}

or tag your template tiddler

$:/tags/ViewTemplate

and then in the template filter for the tag you want with:

<$list filter=‘[is[current]tag[what ever]]’>

Apologies if I’ve not got your question :slight_smile:

3

Before you go too far down the path of “tag conditional viewtemplates” consider using a field.

For example if a tiddler can be only one of a set of different types then use one field that can have only one value.
The following code would be in a tiddler tagged $:/tags/ViewTemplate

<$list filter="[all[current]has[object-type]get[object-type]]" variable=object-type>
   <$list filter="[<object-type>match[todo]]" variable=nul
	    what ever you want to appear on todo items eg: transclude a todo template
	 </$list>
	 <$list filter="[<object-type>match[todo]]" variable=nul
	    duplicate this list widget and change the test for each object type
	 </$list>
</$list>

TYhe advantages of the above method includes

  • Leave tags free for ad hoc use
  • The first test is does the current tiddler have an object-type field with a value otherwise it is all ignored
  • This by definition ends up only applying to tiddlers, not shadows.
  • Only when an object-type is available do the other tests take place
  • Only one of these tests will pass (if you keep the test to “[match[todo]]”

However lets say you want all “object-types” to use a template we can simplify this further.

<$list filter="[all[current]has[object-type]get[object-type]]" variable=object-type>
   <$list filter="[<object-type>addprefix[$:/templates/object-types/]has[title]]" variable=template-tiddler>
     <$transclude tiddler=<<template-tiddler>>/>
	 </$list>
</$list>

So now if the current tiddler has an object-type field with a value it will “attempt to transclude” a matching template tiddler eg: $:/templates/object-types/todo

So in closing rather than use and test a tag set the object-type field on a tiddler and compose its matching template tiddler.

I can package this with some additional features if asked.

4

@knarfix back to your original post.

If you follow this object-type method each of your viewTemplates could test for and offer to create any “constraint definitions” although I am not total sure I understand that term.

5

Many thanks @Ste_W and @TW_Tone for your answers.

I am not yet sure about my path. I think I will need templates will to display my content finally, in one or another way.

My apologies that I can not yet express my intention well, as I am just starting to learn to speak in tw-language :slight_smile:

I had intended to use tags as much as possible. As tags are available in standard tw directly from the edit menu, I planned to control the presentation by tag.

@TW_Tones I will consider your advice to better use a type field for this purpose.

But anyway, I am interested not to build a sophisticated interface with custom menus, but rather let “something” happen just when new field value or tag was entered.

I just found the fieldmangler(perhaps a widget not directly meant to be used by newbies), but maybe it could do what I meant: If a certain tag is added, add certain fields, or the like.

I will keep you posted.
Again, many thanks for the kind welcome and help here

6

sorry @TW_Tones I forgot to answer waht I meant by “contraints”. I thought of rules like that

if a tiddler is tagged “websource”, it needs a field “url”

7

I am building a solution you may use when complete however lets quickly look at your request. Note you have two questions add a field and retrieve a field and maybe you also want to edit the field.

  • The first trick is yo make a view template a tiddler tagged $:/tags/ViewTemplate and it’s content will appear on all tiddlers.
  • First we can make the content conditional based on some information on the current tiddler as per ste
<$list filter="[all[current]tag[what ever]]">
   content here
</$list>

Now inside the above you can add more to display only when your tag exists on the current tiddler

Eg in content here

<$list filter="[all[current]has[fieldname]get[fieldname]]" variable=field-value>
   fieldname <<field-value>> or {{!!fieldname}}
</$list>
<$list filter="[all[current]!has[fieldname]]">
    <$button tooltip="add fieldname to this tiddler">
       <$action-setfield $field="fieldname"  $value="defaultvalue" />
      Add Fieldname
  </$button>
</$list>

The above should be correct but I did not test it.

Minor edit