Boolean Field

Provides a "boolean" field type with an additional state of "not set" in addition to the usual "true/false" or "on/off." A separate display string can be defined for each state. For example, if the field represents the status of a cron job, the three display strings might be:
- Cron job completed without errors
- Cron job completed with errors
- Cron job has not been run.

The corresponding default storage values are 1, 0, and -1.

The field type is integrated with the Rules module.