# Manage chat messages

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After a chat message arrives, you can read its metadata, delete it, and control who can chat through host privileges.

## Read message metadata

Every `onChatNewMessageNotify` callback receives a `ZMVideoSDKChatMessage`. In addition to the sender and content shown in [Core features](/docs/video-sdk/macos/chat/), the message exposes the following fields.

```swift
let messageID = chatMessage.messageID    // String — unique ID; required to delete the message.
let timeMessageWasSent = chatMessage.timeStamp // time_t — when the message was sent.
let isChatToAll = chatMessage.isChatToAll // Bool — true for public messages, false for private.
let currentUserIsSender = chatMessage.isSelfSend // Bool — true if the current user sent the message.
let recipient = chatMessage.receiverUser // ZMVideoSDKUser? — the recipient of a private message; nil when isChatToAll is true.
```

```objectivec
chatMessage.messageID;    // NSString — unique ID; required to delete the message.
chatMessage.timeStamp;    // time_t — when the message was sent.
chatMessage.isChatToAll;  // BOOL — true for public messages, false for private.
chatMessage.isSelfSend;   // BOOL — true if the current user sent the message.
chatMessage.receiverUser; // ZMVideoSDKUser — the recipient of a private message; nil when isChatToAll is true.
```

## Delete a chat message

A user can delete a message they sent, and a host can delete any message in the session. A compliance system can also delete a message under a data-loss-prevention policy. Before exposing a delete control for a given message, ask the SDK whether it can be deleted in the current context.

```swift
guard let chatHelper = ZMVideoSDK.shared()?.getChatHelper() else { return }
let messageID = chatMessage.messageID

if chatHelper.canChatMessageBeDeleted(messageID) {
    let result = chatHelper.deleteChatMessage(messageID)
    if result != .ZMVideoSDKErrors_Success {
        // Surface the error to the user.
    }
}
```

```objectivec
ZMVideoSDKChatHelper *chatHelper = [[ZMVideoSDK sharedVideoSDK] getChatHelper];
NSString *messageID = chatMessage.messageID;

if ([chatHelper canChatMessageBeDeleted:messageID]) {
    ZMVideoSDKErrors result = [chatHelper deleteChatMessage:messageID];
    if (result != ZMVideoSDKErrors_Success) {
        // Surface the error to the user.
    }
}
```

### Listen for deletions

When any message is deleted, the SDK fires `onChatMsgDeleteNotification` on every user's device. Remove the message from your UI in this callback so it stays in sync regardless of who initiated the delete.

```swift
func onChatMsgDeleteNotification(_ chatHelper: ZMVideoSDKChatHelper!, messageID msgID: String!, deleteBy type: ZMVideoSDKChatMessageDeleteType) {
    // Remove the message with id msgID from your UI.
    // Optionally show who removed it using type.
}
```

```objectivec
- (void)onChatMsgDeleteNotification:(ZMVideoSDKChatHelper *)chatHelper messageID:(NSString *)msgID deleteBy:(ZMVideoSDKChatMessageDeleteType)type {
    // Remove the message with id msgID from your UI.
    // Optionally show who removed it using type.
}
```

### Delete-initiator values

`ZMVideoSDKChatMessageDeleteType` tells you who deleted the message.

| Value                                    | Meaning                                                                                 |
| ---------------------------------------- | --------------------------------------------------------------------------------------- |
| `ZMVideoSDKChatMessageDeleteType_None`   | Initialization value, not used in a real callback.                                      |
| `ZMVideoSDKChatMessageDeleteType_BySelf` | The message author deleted their own message.                                           |
| `ZMVideoSDKChatMessageDeleteType_ByHost` | The session host deleted the message.                                                   |
| `ZMVideoSDKChatMessageDeleteType_ByDlp`  | A Data Loss Prevention (DLP) policy removed the message for violating compliance rules. |

## Host control: chat privileges

The session host (or a session manager) can change what kind of chat participants are allowed using `changeChatPrivilege`. Privilege changes fire `onChatPrivilegeChanged` on every user's device. Use that callback to enable or disable your composer.

```swift
guard let chatHelper = ZMVideoSDK.shared()?.getChatHelper() else { return }

// Read the current privilege (any user).
let privilege = chatHelper.getChatPrivilege()

// Change the privilege (host or manager only).
let result = chatHelper.changeChatPrivilege(.publicly)
if result != .ZMVideoSDKErrors_Success {
    // Privilege change was rejected — most commonly because the local
    // user isn't the host or manager.
}
```

```objectivec
ZMVideoSDKChatHelper *chatHelper = [[ZMVideoSDK sharedVideoSDK] getChatHelper];

// Read the current privilege (any user).
ZMVideoSDKChatPrivilegeType privilege = [chatHelper getChatPrivilege];

// Change the privilege (host or manager only).
ZMVideoSDKErrors result = [chatHelper changeChatPrivilege:ZMVideoSDKChatPrivilegeType_Publicly];
if (result != ZMVideoSDKErrors_Success) {
    // Privilege change was rejected — most commonly because the local
    // user isn't the host or manager.
}
```

### Privilege values

`ZMVideoSDKChatPrivilegeType` controls what kinds of chat participants can send.

| Value                                                | Effect                                                            |
| ---------------------------------------------------- | ----------------------------------------------------------------- |
| `ZMVideoSDKChatPrivilegeType_Unknown`                | Uninitialized. Should not appear in a real session.               |
| `ZMVideoSDKChatPrivilegeType_Publicly_And_Privately` | Participants can send public and private chat.                    |
| `ZMVideoSDKChatPrivilegeType_Publicly`               | Participants can send public chat only. Private messaging is off. |
| `ZMVideoSDKChatPrivilegeType_No_One`                 | Chat is fully disabled for non-host participants.                 |

### React to privilege changes

Handle `onChatPrivilegeChanged` and update your composer to match the new privilege.

```swift
func onChatPrivilegeChanged(_ chatHelper: ZMVideoSDKChatHelper!, chatPrivilegeType privilege: ZMVideoSDKChatPrivilegeType) {
    switch privilege {
    case .no_One:
        hideChatComposer()
    case .publicly:
        showComposerWithoutPrivateOption()
    case .publicly_And_Privately:
        showFullComposer()
    default:
        break
    }
}
```

```objectivec
- (void)onChatPrivilegeChanged:(ZMVideoSDKChatHelper *)chatHelper chatPrivilegeType:(ZMVideoSDKChatPrivilegeType)privilege {
    switch (privilege) {
        case ZMVideoSDKChatPrivilegeType_No_One:
            [self hideChatComposer];
            break;
        case ZMVideoSDKChatPrivilegeType_Publicly:
            [self showComposerWithoutPrivateOption];
            break;
        case ZMVideoSDKChatPrivilegeType_Publicly_And_Privately:
            [self showFullComposer];
            break;
        default:
            break;
    }
}
```

If you only need a boolean "is chat available right now" check rather than the specific privilege value, the `isChatDisabled` and `isPrivateChatDisabled` helpers on `ZMVideoSDKChatHelper` are easier to read at the call site.