# init(predicate:) Initializes a rule with the specified predicate. ``` init(predicate: NSPredicate) ``` ## Parameters `predicate` A predicate to be tested when evaluating the rule. ## Return Value A new predicate-based rule object. ## Discussion Rules based on objects typically test information in the [`state`](/documentation/GameplayKit/GKRuleSystem/state) dictionary of the rule system evaluating the rule. For example, the following code creates a rule you might use to determine whether an enemy character in a game behaves aggressively. ```objc // MyNSPredicateRule is a GKNSPredicateRule subclass NSPredicate *healthTest = [NSPredicate predicateWithFormat:@"$player.health > 50"]; MyNSPredicateRule *rule = [MyNSPredicateRule alloc] initWithPredicate:healthTest]; ``` This example presumes the rule system’s state dictionary contains an object for the key `player`, which in turn exposes a numeric value for the key `health`. The [`GKNSPredicateRule`](/documentation/GameplayKit/GKNSPredicateRule) class by itself does nothing in its [`performAction(in:)`](/documentation/GameplayKit/GKRule/performAction(in:)) method—to create actions for predicate-based rules, you must subclass [`GKNSPredicateRule`](/documentation/GameplayKit/GKNSPredicateRule). For more information, see [GameplayKit Programming Guide](https://developer.apple.com/library/archive/documentation/General/Conceptual/GameplayKit_Guide/index.html#//apple_ref/doc/uid/TP40015172). --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)