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# retractFact(_:)

Removes the specified fact from the fact set, and reevaluates the rules in the system’s agenda.

```
func retractFact(_ fact: any NSObjectProtocol)
```

## Parameters

`fact`

An object representing a truth to be rejected by the rule system. For details, see the [`facts`](/documentation/GameplayKit/GKRuleSystem/facts) property.

## Discussion

Calling this method is equivalent to calling the [`retractFact(_:grade:)`](/documentation/GameplayKit/GKRuleSystem/retractFact(_:grade:)) method with a `grade` value of 1.0, thus reducing the fact’s membership grade to zero and removing it from the [`facts`](/documentation/GameplayKit/GKRuleSystem/facts) array.

Upon asserting or retracting any facts, the system reevaluates the rules in its [`agenda`](/documentation/GameplayKit/GKRuleSystem/agenda) list so any rules that depend on changes to the set of facts can perform their actions.

---

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