> For the complete documentation index, see [llms.txt](https://docs.mpush.cloud/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.mpush.cloud/flutter-sdk/ios-setup/custom-replacements.md).

# Custom replacements

To use the custom replacements function yoou will need to update the notification extension cerated in the previous step, here are the steps to follow.

## 1. Create an app group identifier

Go to developer.apple.com -> Certificates, Identifiers & Profiles -> Identifiers. Select App Groups and create a new one.

![](/files/vXeqJzm53DGwbrtDSrKJ)

## 2. Enable App Groups 

You will need then to enable app groups, with the app group created previously, both on developer.apple.com and on the project in XCode, under the Signing & Capabilities section.

You need to do this for the main app and for the notification extension.

## 3. Set the app group identifier

In your `AppDelegate` class set the app group identifier

```swift
SwiftMpushPlugin.appGroupIdentifier = "YOUR_APP_GROUP_ID"
```

## 4. Update the notification extension code

Update your notification extension code to manage the replacements

```swift
    override func didReceive(_ request: UNNotificationRequest, withContentHandler contentHandler: @escaping (UNNotificationContent) -> Void) {
        self.contentHandler = contentHandler
        bestAttemptContent = (request.content.mutableCopy() as? UNMutableNotificationContent)
        
        if let bestAttemptContent = bestAttemptContent {
            manageCustomReplacements(request: request, bestAttemptContent: bestAttemptContent)
            ...
        }
    }

    private func manageCustomReplacements(request: UNNotificationRequest, bestAttemptContent: UNMutableNotificationContent) {
        let appGroupIdentifier = "YOUR_APP_GROUP_ID"
        let customDatakey = "com.mumble.mpush.customData"
        guard let customData = UserDefaults(suiteName: appGroupIdentifier)?.object(forKey: customDatakey) as? [String: String] else {
            return
        }
        
        for (key, value) in customData {
            bestAttemptContent.title = request.content.title.replacingOccurrences(of: key, with: value)
            bestAttemptContent.body = request.content.body.replacingOccurrences(of: key, with: value)
        }
    }
```