---
title: "fetchAndObserveAdherence(usingAggregator:errorHandler:)"
framework: CareKit
role: symbol
role_heading: Instance Method
platforms: [iOS 13.0+, Mac Catalyst 13.0+, watchOS 7.0+]
path: "carekit/ockcalendarcontroller/fetchandobserveadherence(usingaggregator:errorhandler:)"
---

# fetchAndObserveAdherence(usingAggregator:errorHandler:)

Retrieves and observes adherence for each date in the calendar.

## Declaration

```swift
func fetchAndObserveAdherence(usingAggregator aggregator: OCKAdherenceAggregator, errorHandler: ((OCKStoreError) -> Void)? = nil)
```

## Parameters

- `aggregator`: An enumerator value that specifies how to compute adherence for a set of events.