Returns the membership grade of the specified fact.
- iOS 9.0+
- macOS 10.11+
- Mac Catalyst 13.0+
- tvOS 9.0+
An object representing a truth claimed or rejected by the rule system. For details, see the
A value in the range [0.0, 1.0] representing the fact’s membership grade.
Each fact has a membership grade ranging from zero to 1.0, representing variable levels of truth, strength, or confidence for use in fuzzy logic. Use the methods listed in Asserting and Retracting Facts to add or remove facts and set their membership grade—asserting a fact increases its grade, adding it to the array if not present; retracting a set reduces its grade, removing it from the array if its grade drops to zero.
If the specified fact is not in the
facts array, this method returns