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# CHHapticEventParameter

A static parameter value that represents a single property of the haptic pattern.

```
class CHHapticEventParameter
```

## Overview

Event parameters specify values for haptics associated with the event. For example, an intensity event parameter determines how intense the haptic feels when it fires. Event parameters are static; they don’t change over the course of the pattern. To change a parameter value after a haptic has started playing, use a [`CHHapticDynamicParameter`](/documentation/CoreHaptics/CHHapticDynamicParameter) to make an immediate change, or a [`CHHapticParameterCurve`](/documentation/CoreHaptics/CHHapticParameterCurve) to transition smoothly.

![A rising blue line represents how a parameter curve changes the parameter’s value gradually over time, while an orange line shows how dynamic parameters change the parameter’s value immediately.](images/com.apple.corehaptics/media-3197279@2x.png)

When you send a dynamic parameter to the haptic pattern, its value changes immediately, at the specified time. When you send a parameter curve instead, the value changes gradually according to the type of curve you specified.

## Topics

### Creating an Event Parameter

[`-  initWithParameterID:value:`](/documentation/CoreHaptics/CHHapticEventParameter/init(parameterID:value:))

Creates a haptic event parameter from its ID and value.

[`ParameterID`](/documentation/CoreHaptics/CHHapticEvent/ParameterID)

An identifier for an event parameter.

### Specifying an Event Parameter’s Value

[`parameterID`](/documentation/CoreHaptics/CHHapticEventParameter/parameterID)

The haptic parameter ID indicating what type of parameter the current event represents.

[`value`](/documentation/CoreHaptics/CHHapticEventParameter/value)

The value of the parameter.

## Relationships

### Conforms To

[`NSObjectProtocol`](/documentation/ObjectiveC/NSObjectProtocol)

[`CustomDebugStringConvertible`](/documentation/Swift/CustomDebugStringConvertible)

[`CustomStringConvertible`](/documentation/Swift/CustomStringConvertible)

[`Hashable`](/documentation/Swift/Hashable)

[`Equatable`](/documentation/Swift/Equatable)

[`CVarArg`](/documentation/Swift/CVarArg)

### Inherits From

[`NSObject-swift.class`](/documentation/ObjectiveC/NSObject-swift.class)

---

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