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# attackTime

The time at which a haptic pattern’s intensity begins increasing.

```
static let attackTime: CHHapticEvent.ParameterID
```

## Discussion

This parameter can be an event parameter or a dynamic parameter. An event parameter indicates that the haptic begins increasing in intensity at the set time, where time `0` indicates now, or the current time.

A dynamic value indicates that the time at which ramp-up begins can change. For example, a value of `0` indicates that the attack time is at its default value. Positive values up to `1.0` increase the attack time exponentially, while negative values down to `-1.0` decrease the attack time exponentially. Haptic intensity responds to this parameter.

![A series of lines showing how a haptic pattern ramps up in intensity for various values of attack.](images/com.apple.corehaptics/media-3235478@2x.png)

---

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