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This is the new Docs for Chat SDK v4 for iOS. To see the previous Docs, click here.

Display Open Graph tags in a message

The Chat SDK supports the URL link preview for both open channels and group channels when a message text contains the URL of a web page. This feature is turned on by default for Sendbird applications. If this isn't available for your Sendbird application, see this page and contact us on the Sendbird Dashboard to enable the feature.

Note: The above image shows a chat view completed with our UIKit components. Your client app's channel view may look different depending on channel type and UI settings.


OGMetaData

If a BaseMessage object includes a valid URL of a website, the object can contain OGMetaData, a class that holds OG metadata information 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 nil.

List of properties

Property nameDescription

title

The title of the OG object as it should appear within the graph. The value can be nil.

url

The canonical URL of the object that can be used as its permanent ID in the graph. The value can be set to nil.

desc

The description of the object. The value can be set to nil.

defaultImage

An OGImage instance that contains information about the image that the Open Graph points to. OGImage also holds its own properties such as type, URL, and size. However, the value can be set to nil.


OGImage

The OGImage instance holds image-related data for an OGMetaData object. OGImage can also have six optional structured properties of URL, secure URL, type, width, height, and alt. Except for width and height, other fields such as URL, secure URL, type, and alt can be set to nil. If the target website doesn’t provide width and height data, the value of those two fields are set to 0.

List of properties

Property nameDescription

url

The URL of an image object within the Open Graph. The value can be set to nil.

secureURL

An alternative URL to use if the webpage requires HTTPS. The value can be set to nil.

type

A media type or MIME type of this image. The value can be set to nil.

width

The number of pixels horizontal. When the value is unavailable, this method returns 0.

height

The number of pixels vertical. When the value is unavailable, this method returns 0.

alt

The description of what is in the image, not a caption of the image. The alt attribute is designed to provide a fuller context of the OGImage object and help users better understand it when they can’t load or see the image. The value can be set to nil.


How it works

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 channel(_:didReceive:) method in the channel event delegate of the SDK. On the other hand, the message sender will do the same through channel(_:didUpdate:).

Displaying an OG metadata object is available for two subtypes of BaseMessage: UserMessage and AdminMessage. If the content of either a UserMessage or AdminMessage object includes a web page URL containing OG metadata, the channel(_:didReceive:) method returns OGMetaData and OGImage objects.

If Sendbird server doesn’t have cache memory of the OG metadata of the given URL, ogMetaData can be nil 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 channel(_:didReceive:) method. When the server completes fetching, the channel(_:didUpdate:) method will be called and the message with its OGMetaData object will be delivered to the recipients’ client app. However, if Sendbird server has already cached the OG metadata of the URL, ogMetaData returns the message and its OGMetaData object instantly and the channel(_:didUpdate:) method won’t be called.

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

channel.sendUserMessage(params: params) { userMessage, error in
    guard error == nil else {
        // Handle error.
        return
    }
}

// ViewController.swift
// Receive a user message containing OG metadata of the web page
// through a channel event delegate.
func channel(_ channel: BaseChannel, didReceive message: BaseMessage) {
    if let ogMetaData = message.ogMetaData {
        // You can create and customize the URL link preview
        // by using the Open Graph metadata of the message.
        let url = ogMetaData.url
    } else {
        // If the message.ogMetaData is nil,
        // wait until the channel(_:didUpdate:) method receives a callback from the Sendbird server.
    }
}

func channel(_ channel: BaseChannel, didUpdate message: BaseMessage) {
    if let ogMetaData = message.ogMetaData {
        // You can create and customize the URL link preview
        // by using the Open Graph metadata of the message.
        let url = ogMetaData.url
    }
}