init(predicate:)

Declaration

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 NSPredicate objects typically test information in the 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.

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 class by itself does nothing in its performAction(in:) method—to create actions for predicate-based rules, you must subclass GKNSPredicateRule.

For more information, see GameplayKit Programming Guide.