---
title: formatSubstring
framework: OSLog
role: symbol
role_heading: Instance Property
platforms: [iOS 15.0+, iPadOS 15.0+, Mac Catalyst 15.0+, macOS 10.15+, tvOS 15.0+, visionOS 1.0+, watchOS 8.0+]
path: oslog/oslogmessagecomponent/formatsubstring
---

# formatSubstring

The text immediately preceding a placeholder.

## Declaration

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

## Discussion

Discussion The formatSubstring property can be an empty string if there is nothing between two placeholders, or if it is between the placeholder and the bounds of the string.

## See Also

### Reading the Message Component

- [placeholder](oslog/oslogmessagecomponent/placeholder.md)