PREFIX-change

Summary

• [PREFIX-change marker][condition] VALUE [/condition] TEXT [/PREFIX-change marker]

Description

Sets up a breaking sequence that occurs when the contents of the [condition] VALUE [/condition] change.  The most common use is a category break to nest or place headers.

The region is only output when a field or other repeating value between [condition] and [/condition] changes value.  This allows indented lists similar to database reports to be easily formatted.  The repeating value must be a tag interpolated in the search process, such as [PREFIX-field] or [PREFIX-field table column].  If you need access to Interchange tags then you can use [PREFIX-calc] with a $Tag-foo() (Perl) call.

Of course, this will only work as you'd expect if the search results are properly sorted.

The "marker" parameter is mandatory, and is also arbitrary;  Any "marker" can be selected, as long as the name same name is used in both the start and end tags.

The value to be tested is contained within a [condition] VALUE [/condition] tag pair.  The [PREFIX-change] tag also processes an optional "[else]...[/else]" block, which can be used to output some text when the VALUE has not changed.

Here is a simple example for a search list that has a field category and subcategory associated with each item:

The above should put out a table that only shows the category and subcategory once, while showing the name for every product.  The " " will prevent "empty" cells from messing up the table display.

You should also know that this loop sub-tag will nest.  For example:

Closing tag syntax

The closing tag syntax is slightly different from most other container tags.  Most container tags use a format such as "[tagname params]...[/tagname]", whereas this loop sub-tag uses "[tagname param]...[/tagname param]".  For example: