Custom widget parameters values validation

#1

Hi!

I’m working on a custom widget and I want to validate user input values for parameters. For example, the $default parameter should contain a default value for the widget when the target field is missing or blank, just like <$edit-text> widget’s default parameter.

I first tried to use a <$parameter> widget, but default value for parameters are only used when the widget attribute value is missing, so I can’t use it to validate any user-defined value.

So I ended up using this pattern:

\function init.default()
  =[<$default>!is[blank]]
  =[<now "YYYY0MM0DD">]
  :filter[<currentTiddler>format:date[YYYY0MM0DD]match<currentTiddler>]
  +[first[]]
\end

\widget $my.widget($default)
<$let
 myDefault=<<init.default>>
>

<!-- relevant code using <<myDefault>> here... -->

</$let>
\end $my.widget

My real widget has 6+ parameters, all of which must be validated, leading to a lot of code verbosity. Did any of you work on this kind of problems? Do you have alternative code patterns to showcase? Or enhancement suggestions?

Thanks in advance

Fred

#2

I think in this case verbosity is your friend, because it will be easier to maintain in the future. The only one, which sees the verbosity is a developer. So that should not be a problem for your users.

I do not understand, why you have a $default attribute name. They are used by the GenesisWidget and there they are reserved for the core. So IMO you should not use it for custom widgets.

You could use _default if you need to.

1 Like
#3

Thanks @pmario for your answer.

Well it’s an error! :sweat_smile: I wanted my widget interface to be like an <$edit-text> and until I checked docs to write this topic I really thought the parameter name was $default, not default! Oops! I’ll change it, thanks for the advice.

Fred

#4

If you want to you can move the function inside and then you don’t need the let statement.
You can also simplify your validation logic a bit by re-structuring the filter since validating the date format will handle blanks too and ~ will only be processed if the previous filter hasn’t returned a result
eg.

\widget $my.widget(default)
  \function myDefault() [<default>format:date[YYYY0MM0DD]match<default>] ~[<now "YYYY0MM0DD">]

  <<myDefault>>

\end $my.widget

or for more verbose:

\widget $my.widget(default)
  \function myDefault()
    [<default>format:date[YYYY0MM0DD]match<default>]
    ~[<now "YYYY0MM0DD">]
  \end myDefault

  <<myDefault>>

\end $my.widget

Testing:

* <$my.widget/>
* <$my.widget default=""/>
* <$my.widget default="20250202" />
* <$my.widget default="Not a date" />
  • 20250310
  • 20250310
  • 20250202
  • 20250310
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