listField Mode

Using the checkbox widget in list mode requires the listField attribute to specify the name of a field containing a list. The checked attribute specifies the value that should be present or absent in the list when the checkbox is checked or unchecked respectively. If checked is absent (or empty) but unchecked is present, then the logic will be inverted: the checkbox will be checked when the unchecked value is missing from the list, and unchecked when the unchecked value is found in the list. If both checked and unchecked are present, the checkbox will work like a toggle, replacing the checked value with the unchecked value and vice-versa. Finally, if neither checked nor unchecked is specified, the checkbox will be checked if the field has anything in it, but unchecked if the field is missing or empty. (This is rarely useful. Most of the time you want to specify checked or unchecked or both.)

The default attribute is used as a fallback for the checkbox state if the field is not defined.

The following table summarizes the possible combinations:

This example creates a checkbox that is checked if the list field named colors contains green and unchecked if the field contains red. If the field is undefined, or if neither green nor red appears in the field, then it defaults to green, meaning that the checkbox will be checked.

<$checkbox listField="colors" checked="green" unchecked="red" default="green"> Is "green" in colors?</$checkbox><br />''colors:'' {{!!colors}}

Try editing the colors field of this tiddler to see how the example changes.