---
title: MFMessageComposeViewController.TextMessageAvailabilityDidChangeMessage.Subject
framework: messageui
role: symbol
role_heading: Type Alias
path: messageui/mfmessagecomposeviewcontroller/textmessageavailabilitydidchangemessage/subject
---

# MFMessageComposeViewController.TextMessageAvailabilityDidChangeMessage.Subject

The notification subject type

## Declaration

```swift
typealias Subject = MFMessageComposeViewController
```

## Discussion

Discussion This notification is always posted with a nil object, so instance filtering is not applicable. The type provides namespace scoping for the identifier.