Open channel: Advanced

This page explains the advanced features for open channels.

You can send an admin message to an open channel using Sendbird Dashboard or Chat Platform API. To send the admin message through your dashboard, on the Chat > Open channels, select an open channel, find a message box below, click the Admin message tab, and then write your message in the box. An admin message is limited to 1,000 characters.

You have the option to create further actions in a channel by using extra data in a message. You can add one or more key-values items to a message which you can save, update, or remove, when necessary. Based on those items, you can design and implement several different actions such as measuring user engagement within a chosen time limit through polls or counting how many times a message has been copied by participants.

Note: For the quality of performance, every Sendbird application has its own limits to how many key-values items you can add to a single message, as well as the maximum number of values an item can have. If you would like more information on these limits, contact our sales team.

// When a message has been successfully sent to a channel, create items with keys.
[openChannel createMessageMetaArrayKeysWithMessage:MESSAGE keys:@[@"referees", @"games"] completionHandler:^(SBDBaseMessage * _Nullable message, SBDError * _Nullable error) {
    if (error != nil) {
        // Handle error.
    }


}];

// Adding values to specific items by their keys.
NSDictionary *valuesToAdd = @{
    @"referees": @[@"John", @"Brandon", @"Harry", @"Jay"],
    @"games": @[@"soccer", @"baseball", @"basketball"],
};

[openChannel addMessageMetaArrayValuesWithMessage:MESSAGE keyValues:valuesToAdd completionHandler:^(SBDBaseMessage * _Nullable message, SBDError * _Nullable error) {
    if (error != nil) {
        // Handle error.
    }


}];

// Removing existing values of specific items by their keys.
NSDictionary *valuesToRemove = @{
    @"referees": @[@"Brandon", @"Jay"],
};

[openChannel removeMessageMetaArrayValuesWithMessage:MESSAGE keyValues:valuesToRemove completionHandler:^(SBDBaseMessage * _Nullable message, SBDError * _Nullable error) {
    if (error != nil) {
        // Handle error.
    }


}];

// Deleting items by their keys.
[openChannel deleteMessageMetaArrayKeysWithMessage:MESSAGE keys:@[@"referees", @"games"] completionHandler:^(SBDBaseMessage * _Nullable message, SBDError * _Nullable error) {
    if (error != nil) {
        // Handle error.
    }


}];

To get the key-values items of a message, read the message.metaArrays.

The Chat SDK supports the URL link preview when a message text contains the URL of a web page.

Note: This feature is turned on by default for Sendbird applications. If this isn't available for your Sendbird application, contact our support team to enable the feature.

To view the image in full screen, click on the

If a SBDBaseMessage object includes a valid URL of a website, the object can contain SBDOGMetaData, a class that holds the OG metadata such as title, URL, description, and default image of an OG object.

Note: Some websites don’t provide the OG metadata. In that case, even though the OG protocol states them as requirements, all of the four properties can be null.

A SBDOGImage, the image contained in a SBDOGMetaData object, is a class that holds image-related data for the SBDOGImage object. The SBDOGImage class can also have its own optional structured properties of URL, secure URL, type, width, height, and alt.

Note: Except for width and height, other fields such as URL, secure URL, type, and alt can be null. If the target website doesn’t provide width and height data, the value of those two fields are set to 0.

If a user sends a message with a web page URL and the linked web page possesses Open Graph (OG) tags, or OG metadata, Sendbird server parses the message content, extracts the URL in the message, gets the OG metadata from it, and creates an OG metadata object for the message. Then message recipients will get the parsed message with its OG metadata through the didReceiveMessage: method in the channel event delegate of the SDK. On the other hand, the message sender will do the same through the didUpdateMessage:.

Displaying an OG metadata object is available for two subtypes of a SBDBaseMessage: SBDUserMessage and SBDAdminMessage. If the content of either a SBDUserMessage or SBDAdminMessage object includes a web page URL containing OG metadata, the didReceiveMessage: method returns SBDOGMetaData and SBDOGImage objects.

If Sendbird server doesn’t have cache memory of the OG metadata of the given URL, the SBDBaseMessage.ogMetaData can be null due to the time it takes to fetch the OG metadata from a remote web page. In the meantime, the message text containing the URL will be delivered first to message recipients’ client app through the didReceiveMessage: method. When the server completes fetching, the didUpdateMessage: method will be called and the message with its SBDOGMetaData object will be delivered to the recipients’ client app. However, if Sendbird server has already cached the OG metadata of the URL, the SBDBaseMessage.ogMetaData returns the message and its SBDOGMetaData object instantly and the didUpdateMessage: method won’t be called.

// Send a user message containing the URL of a web page.
var params = SBDUserMessageParams()
params.message = "sendbird.com"
...

openChannel.sendUserMessage(with: params, completionHandler: { (userMessage, error) in
    guard error == nil else {
        // Handle error.
    }

    ...
})

// ViewController.swift
// Receive a user message containing OG metadata of the web page through a channel event delegate.
func channel(_ sender: SBDBaseChannel, didReceive message: SBDBaseMessage) {
    if message.ogMetaData != nil {
        // You can create and customize the URL link preview by using the Open Graph metadata of the message.
        let url = message.ogMetaData.url
        let width = message.ogMetaData.width

        ...
    } else {
        // If the `message.ogMetaData` is `nil`, wait until the `didUpdate` method receives a callback from Sendbird server.
    }


}

func channel(_ sender: SBDBaseChannel, didUpdate message: SBDBaseMessage) {
    if message.ogMetaData != nil {
        // You can create and customize the URL link preview by using the Open Graph metadata of the message.
        let url = message.ogMetaData.url
        let width = message.ogMetaData.width

        ...
    }


}

When creating an open channel, you can additionally specify a custom channel type to subclassify open channels. This custom type takes on the form of a NSString, and can be useful in searching or filtering open channels.

The data and customType properties of a channel object allow you to append information to your channels. While both properties can be used flexibly, common examples for the customType include categorizing open channels into School or Work.

SBDOpenChannel.createChannel(withName: NAME, coverUrl: COVER_URL, data: DATA, operatorUsers: OPERATOR_USERS, customType: CUSTOM_TYPE, progressHandler: nil, completionHandler: { (openChannel, error) in
    guard error == nil else {
        // Handle error.
    }

    ...
})

To get a channel's custom type, read the openChannel.customType.

When sending a message, you can additionally specify a custom message type to subclassify messages. This custom type takes on the form of a NSString, and can be useful in searching or filtering messages.

The data and customType properties of a message object allow you to append information to your messages. While both properties can be used flexibly, common examples for the customType include categorizing message groups into Notes or Contacts.

To embed a custom type into your message, assign a value to the customType under the SBDUserMessageParams or SBDFileMessageParams object. Then, pass the specified object as an argument to the parameter in the sendUserMessageWithParams:completionHandler: or sendFileMessageWithParams:completionHandler: method.

var params = SBDUserMessageParams()
params.message = MESSAGE
params.customType = CUSTOM_TYPE
...

openChannel.sendUserMessage(with: params, completionHandler: { (userMessage, error) in
    guard error == nil else {
        // Handle error.
    }

    ...
})

To get a message's custom type, read the message.customType.

You can search for specific open channels by adding keywords to a SBDOpenChannelListQuery instance. There are two types of keywords: a Name and a URL. The code sample below shows the query instance which returns a list of open channels that partially match the specified Name keyword in the names of the channels.

let listQuery = SBDOpenChannel.createOpenChannelListQuery()
listQuery.channelNameFilter = "Sendbird"

listQuery.loadNextPage(completionHandler: { (openChannels, error) in
    guard error == nil else {
        // Handle error.
    }

    // Through "openChannels" parameter of the callback method, which Sendbird server has passed a result list to,
    // A list of open channels that partially match 'Sendbird' in their names is returned.

})

The following shows the query instance which returns a list of open channels that partially match the specified URL keyword in the URLs of the channels.

let listQuery = SBDOpenChannel.createOpenChannelListQuery()
listQuery.channelUrlFilter = "seminar"

listQuery.loadNextPage(completionHandler: { (openChannels, error) in
    guard error == nil else {
        // Handle error.
    }

    // Through "openChannels" parameter of the callback method, which Sendbird server has passed a result list to,
    // a list of open channels that partially match 'seminar' in their names is returned.

})

Using the setCustomTypeFilter: like the following, you can also search for open channels with a specific custom type.

let listQuery = SBDOpenChannel.createOpenChannelListQuery()
listQuery.customTypeFilter = "movie"

listQuery.loadNextPage(completionHandler: { (openChannels, error) in
    guard error == nil else {
        // Handle error.
    }

    // Through "openChannels" parameter of the callback method, which Sendbird server has passed a result list to,
    // a list of open channels with a 'movie' custom type is returned.

})

When sending an image file, you can determine whether to create thumbnails of the image to fetch and render into your UI. You can specify up to 3 different dimensions to generate thumbnail images in for supporting various display densities.

Note: Supported file types are files whose media type is image/* or video/*. The Chat SDK doesn't support creating thumbnails when sending a file message with a file URL.

The sendFileMessageWithParams:completionHandler: method requires passing a SBDFileMessageParams object as an argument to a parameter, containing a NSArray of SBDThumbnailSize objects which each specify the maximum values of width and height of a thumbnail image with its makeWithMaxCGSize: or makeWithMaxWidth:maxHeight: constructors. The completionHandler: callback subsequently returns a NSArray of SBDThumbnail objects that each contain the URL of the generated thumbnail image file.

var thumbnailSizes = [SBDThumbnailSize]()

// Creating and adding a SBDThumbnailSize object (allowed number of thumbnail images: 3).
thumbnailSizes.append(SBDThumbnailSize.make(withMaxCGSize: CGSize(width: 100.0, height: 100.0))!)
thumbnailSizes.append(SBDThumbnailSize.make(withMaxWidth: 200.0, maxHeight: 200.0)!)

var params = SBDFileMessageParams()

params.file = FILE
params.fileName = FILE_NAME
params.fileSize = FILE_SIZE
params.mimeType = MIME_TYPE
params.thumbnailSizes = thumbnailSizes  // Set a SBDThumbnailSize object to a SBDFileMessageParams object.

openChannel.sendFileMessage(with: params, completionHandler: { (fileMessage, error) in
    guard error == nil else {
        // Handle error.
    }

    let first = fileMessage?.thumbnails?[0]
    let second = fileMessage?.thumbnails?[1]

    let maxSizeFirst = first?.maxSize   // 100
    let maxSizeSecond = second?.maxSize // 200

    let urlFirst = first?.url
    let urlSecond = second?.url


})

A thumbnail image is generated evenly to fit within the bounds of maxWidth and maxHeight, which are provided through the constructor. Note that if the original image is smaller than the specified dimensions, the thumbnail isn't resized. The url returns the location of the generated thumbnail file within Sendbird server.

This file encryption feature prevents users without access from opening and reading encrypted files that have been shared within a group of users. When this feature is turned on, all types of sent files and thumbnail images will be first uploaded to Sendbird server, and then encrypted by AES256.

In an open channel, encrypted files and thumbnail images will be decrypted and accessed securely only by the participants. Anyone outside of the channel and application will not have access to those files and thumbnail images. The following explains how this data security works and what to do at the SDK level to apply it to your client apps.

The Sendbird system enables secure encryption and decryption of files by generating and distributing an opaque and unique encryption key for each user. An encryption key is managed internally by the system, and is valid for 3 days. It is generated every time the user logs in to Sendbird server through the Chat SDK, which then gets delivered to the Chat SDK from the server.

When the Chat SDK requests an encrypted file by its URL, the parameter auth should be added to the URL to access the file, which is specified with an encryption key of the user such as ?auth=RW5jb2RlIHaXMgdGV4eA==. With the specified key in the auth, Sendbird server first decrypts the file, then checks if the user is participating in the open channel, and finally, allows the user to access and open the file in the channel.

This can be easily done by retrieving the fileMessage.url property, which returns the unique file URL containing the parameter auth with an encryption key of the current user.

This feature allows you to customize the number of messages a participant can send in an open channel per second. By doing so, all excess messages from a participant will be deleted and only the number of messages allowed to be sent per participant per second will be delivered. This feature protects your app from some participants spamming others in the channel with the same messages.

Note: Our default system setting is 5 messages per second. This limit can be manually adjusted only from our side. Contact our sales team for more information.

You can use this feature to customize the number of messages displayed in an open channel per second. By doing so, you can adjust the pace of the conversation in a chat so that the participants can read the messages more clearly. In fact, each participant's channel will display the messages they have sent and those that other participants have sent up to this limit in chronological order.

Note: Our default system setting is 5 messages per second. This limit can be manually adjusted only from our side. Contact our sales team for more information.

It is possible for text messages to be sent in different languages through the Sendbird's auto-translation feature. When sending a text message, set a NSArray of language codes to a SBDUserMessageParams object and then pass the object as an argument to a parameter in the sendUserMessageWithParams:completionHandler: method to request translated messages in the corresponding languages.

Note: Message auto-translation is powered by Google Cloud Translation API recognition engine. Find language codes supported by the engine in the Miscellaneous page or visit the Language Support page in Google Cloud Translation.

var params = SBDUserMessageParams()
...
params.targetLanguages = ["es", "ko"]   // Spanish and Korean

openChannel.sendUserMessage(with: params, completionHandler: { (userMessage, error) in
    guard error == nil else {
        // Handle error.
    }

    ...
})

You can retrieve translations of a text message using the userMessage.translations property which has a NSArray object containing the language codes and translations.

func channel(_ sender: SBDBaseChannel, didReceive message: SBDBaseMessage) {
    If let message = message as? SBDUserMessage {
        let esTranslatedMessage = message.translations["es"]    // Spanish


        // Display translation in UI.
    }
}

Using the translateUserMessage:targetLanguages:completionHandler: method, you can also translate an already sent text message into other languages for your specific needs.

Note: Message on-demand translation is powered by Google Cloud Translation API recognition engine. Find language codes supported by the engine in the Miscellaneous page or visit the Language Support page in Google Cloud Translation.

let targetLanguages = ["es", "de"]

// The USER_MESSAGE below indicates a SBDUserMessage object which represents an already sent or received text message.
openChannel.translateUserMessage(USER_MESSAGE, targetLanguages: targetLanguages, completionHandler: { (userMessage, error) in
    guard error == nil else {
        // Handle error.
    }

    let translations = (userMessage as! SBDUserMessage).translations
    let esTranslatedMessage = translations["es"]    // Spanish
    let deTranslatedMessage = translations["de"]    // German
    ...
    // Display translations in UI.
})

Based on this method, you can implement features such as real-time or instant translation to your app. You can also implement to only translate a selected message into preferred languages.