---
title: key
framework: foundation
role: symbol
role_heading: Type Property
path: foundation/progressmanager/property/key
---

# key

A unique identifier for this property type.

## Declaration

```swift
static var key: String { get }
```

## Return Value

Return Value A unique string identifier for this property type.

## Discussion

Discussion The key should use reverse DNS style notation to ensure uniqueness across different frameworks and applications.