Query: How Do You Pass Parameters?

[TiddlyTweeter]

I try to be brief ...

\define thing(thingie:"wotnot")

 User enters ...

<<thing "hammer">>

 I have a second macro ...

\define dostuff(thingie:"wotnot")

How do I get "dostuff" to know the parameter value is now "hammer", not "wotnot"?

This is probably awfully unclear!

Trying to grasp basics.

TT

[Mark S.]

What you're not showing, which I think must be the missing step, is how you call "dostuff". If you call it like

<<dostuff "hammer">>

it should use "hammer", just like "thing" did. So not sure what the problem is, unless you're calling dostuff in relation to "thing", somehow.

[TiddlyTweeter]

I *think* I get it. I'll try & see.

TT

[TW Tones]

TT,

This would be worth a simple summary, to guide users. Since I am not so sure about your question, I suspect you just had a "mind block".

[Edit Minor typos]

In your case 

<<dostuff "hammer">> will change $thingie$ to be "hammer"

The following is a little verbose because it forms part of a future blog post

Basically 

• if you want to use parameters in a macro they need to be named in the braces macroname(p1 p3) the access them with $p1$ $p2$
• You can set a default value for parameters with (p1:"defaultvalue",p2)
• When calling the macro the `<<macroname>>` is a little limited, only literal strings can be used ` <<macroname "value1" "Value2">>`
• Here we are relying on the order of the parameters
• If you want to pass parameters out of order you need to name them, for example we may want to use the default for p1 and pass only value2
• We use `<<macroname p2:"value2">>` uses the same format as inside the definition braces ().
• The only way to pass variables and field values to a macro is the macrocall widget
• `<$macrocall $name="macroname" p1={{!!fieldname)) p2=<<variable>> p3=<<wikifiedmacro>>/>`
• However variables in the calling wikitext can be accessed in macros with $(varname)$ without being added to the parameters
• Whenever something is wrapped in $ signs the value is replaced before the wikitext/macro is evaluated., ro $values$ or $(varname)$ may need to be quotes etc..
  
• `<$tiddler tiddler="[[($currentTiddler$)]]">...` (only in macro definitions)
• There may be cases where you want to use one of the parameters as if it were a variable 
• `<$tiddler tiddler=<<__p2__>> >...`

Other ways to set default value for parameters

\define macroname(p1 p2)
<$set name=p1 value="$p1$"emptyValue="defaultValue">

Use <<p1>> not $p1$

</$set>
\end

See how this converts the parameter to a variable?

The default value can be other references or macros as well.

You can even set the `p1` variable multiple times

<$set name=p1 value="$p1$"emptyValue="$(varname)$">
<$set name=p1 value=<<p1>>"emptyValue="defaultValue">

Use <<p1>> not $p1$

</$set></$set>

In this case if no parameter is provided, and the first emptyValue="$(varname)$" is itself empty

Then the defaultvalue will be set

Regards

TW Tones