Load previous messages

By using the loadNextPage(completionHandler:) method of a PreviousMessageListQuery instance which returns a list of BaseMessage objects, you can retrieve a set number of previous messages in a channel. With the returned list, you can display the past messages in your UI once they have loaded.

Open channel

Swift

class CustomViewController: ViewController {
    var channel: OpenChannel?
    var query: PreviousMessageListQuery?

    func createQuery() {
        // There should be one single instance per channel.
        self.query = channel?.createPreviousMessageListQuery { params in
            // The params is the PreviousMessageListQueryParams object.
            params.customTypeFilter = "greeting"
            params.limit = LIMIT
            params.reverse = REVERSE
        }
    }

    func loadNextPage() {
        // Retrieve previous messages.
        self.query?.loadNextPage(completionHandler: { messages, error in
            guard error == nil else {
                // Handle error.
                return
            }
        })
    }
}

Group channel

Swift

class CustomViewController: ViewController {
    var channel: GroupChannel?
    var query: PreviousMessageListQuery?

    func createQuery() {
        // There should be one single instance per channel.
        self.query = channel?.createPreviousMessageListQuery(paramsBuilder: { params in
            // The params is the PreviousMessageListQueryParams object.
            params.customTypeFilter = "greeting"
            params.limit = LIMIT
            params.reverse = REVERSE
        })
    }

    func loadNextPage() {
        // Retrieve previous messages.
        self.query?.loadNextPage(completionHandler: { messages, error in
            guard error == nil else {
                // Handle error.
                return
            }
        })
    }
}

PreviousMessageListQueryParams

Property name	Type	Description
limit	UInt	Specifies the number of results to return per call. Acceptable values are `1` to `100`, inclusive. The recommended value for this parameter is `20`.
reverse	Bool	Determines whether to sort the retrieved messages in reverse order. If set to `true`, messages are returned from the most recent to the oldest. (Default: `false`)

The limit property determines how many messages to include in a returned list. The PreviousMessageListQuery instance itself does pagination of a result set according to the value of the limit property, and internally manages a token to retrieve the next page in the result set.

Each time the loadNextPage(completionHandler:) method is called, the instance retrieves a set number of messages in the next page and then updates the token's value to complete the current call and prepare the next call. Before calling the loadNextPage(completionHandler:) method again, you should receive a success callback through the completionHandler first.

If you create a new query instance and call the loadNextPage(completionHandler:) method, a set number of the most recent messages are retrieved because its token has nothing to do with the previously created instance. So we recommend that you create a single query instance and store it as a member variable for traversing through the entire message history.

Sample app