---
title: "init(_:dataHandler:)"
framework: healthkit
role: symbol
role_heading: Initializer
path: "healthkit/hkelectrocardiogramquery/init(_:datahandler:)"
---

# init(_:dataHandler:)

Creates a new electrocardiogram query object.

## Declaration

```swift
convenience init(_ ecg: HKElectrocardiogram, dataHandler: @escaping (HKElectrocardiogramQuery, HKElectrocardiogramQuery.Result) -> Void)
```

## Parameters

- `ecg`: The electrocardiogram sample whose voltages you want to access.
- `dataHandler`: A block that the query calls repeatedly to return the voltage data. The handler takes the following parameters:

## Discussion

Discussion When you run the query, it calls the data handler once for each voltage measurement, passing a HKElectrocardiogramQuery.Result.measurement(_:) instance that contains the voltage data. After it has sent all the voltage measurements, it calls the data handler one last time, passing HKElectrocardiogramQuery.Result.done. If an error occurs, it stops collecting voltage data and passes HKElectrocardiogramQuery.Result.error(_:) instead.