---
title: identifier
framework: foundation
role: symbol
role_heading: Instance Property
path: foundation/nsbackgroundactivityscheduler/identifier
---

# identifier

A unique reverse DNS notation string, such as com.example.MyApp.updatecheck, that identifies the activity.

## Declaration

```swift
var identifier: String { get }
```

## Discussion

Discussion This string should remain constant for an activity across launches of your app because the system uses this unique identifier to track the number of times the activity has run and to improve the heuristics for deciding when to run it again in the future. nil and zero-length strings are not allowed. See Configure Scheduler Properties.

## See Also

### Related Documentation

- [init(identifier:)](foundation/nsbackgroundactivityscheduler/init(identifier:).md)

### Background Scheduler Attributes

- [repeats](foundation/nsbackgroundactivityscheduler/repeats.md)
- [interval](foundation/nsbackgroundactivityscheduler/interval.md)
- [qualityOfService](foundation/nsbackgroundactivityscheduler/qualityofservice.md)
- [shouldDefer](foundation/nsbackgroundactivityscheduler/shoulddefer.md)
- [tolerance](foundation/nsbackgroundactivityscheduler/tolerance.md)