Extra Data
Extra Data is additional information that can be added to the default data of Stream. It is a dictionary of key-value pairs that can be attached to messages, users, channels, and pretty much almost every domain model in the Stream SDK.
On iOS, the Extra Data is represented by the following dictionary, [String: RawJSON]. The RawJSON is an enum that can be represented by different types of values. It can be a String, Number, Boolean, Array, Dictionary, or null. In the end, this is to make the dictionary strongly typed so that it is safer and easier to use. The code snippet below shows the simplified implementation of RawJSON.
indirect enum RawJSON: Codable, Hashable {
case number(Double)
case string(String)
case bool(Bool)
case dictionary([String: RawJSON])
case array([RawJSON])
}
Adding Extra Data
Adding extra data can be done through the Server-Side SDKs or through the Client SDKs. In the iOS Stream Chat SDK, you can add extra data when creating/updating a message, user, channel, or any other model through our controllers.
As a simple example, let's see how you can add a new email field to the currently logged user.
let currentUserController = client.currentUserController()
currentUserController.updateUserData(
name: "John Doe",
imageURL: nil,
userExtraData: ["email": .string("john.doe@example.com")],
completion: nil
)
For a more complete example now, let's imagine you want to add ticket information to a message.
let extraData: [String: RawJSON] = [
"ticket": .dictionary([
"name": .string("Rock Concert"),
"price": .double(20)
])
]
let channelController = client.channelController(for: yourChannelId)
channelController.createNewMessage(text: "A new message", extraData: extraData)
Since RawJSON implements ExpressibleByDictionaryLiteral, you can simplify the example above like this:
let extraData: [String: RawJSON] = [
"ticket": [
"name": .string("Rock Concert"),
"price": .double(20)
])
]
Note: This is only available on 4.19.0+ versions of the SDK.
Reading Extra Data
All of the most important domain models in the SDK have an extraData property that you can read the additional information added by your app.
Since the 4.19.0 version of the SDK, you can read extra data properties very easily. The following code snippet shows how to get an email from a user's extra data.
let email = user.extraData["email"]?.stringValue ?? ""
print(email)
If you are using an SDK version below 4.19.0, this is how you would read the email from the extra data:
let extraData = user.extraData
var email: String {
guard case .string(let value) = extraData["email"] else { return "" }
return value
}
In order to access the email even more easily, you can extend our models to provide an extra property, in this case, you can add an email property to the ChatUser model like this:
extension ChatUser {
var email: String? {
extraData["email"]?.stringValue
}
}
To see how you can get data with different types from extra data, we can pick the example of the ticket information again and see how you can get it from extra data.
let ticket = message.extraData["ticket"]?.dictionaryValue
let name = ticket?["name"]?.stringValue ?? ""
let price = ticket?["price"]?.doubleValue ?? 0.0
As you can see above, each type of value can be easily accessible from an extra data property. The SDK will try to convert the raw type to a strongly typed value and return it if the property exists, and if the type is correct. Below is the list of all values supported:
stringValue: String?numberValue: Double?boolValue: Bool?dictionaryValue: [String: RawJSON]?arrayValue: [RawJSON]?stringArrayValue: [String]?numberArrayValue: [Double]?boolArrayValue: [Bool]?
Advanced Example
Most likely your app has more complex data structures compared to the ones described above. So, let's see an example of how you could map your domain models to extra data and vice-versa by imagining that a message can have details of a booking flight.
struct BookingFlight {
let flightNumber: Double
let departureDate: Date
let arrivalDate: Date
let price: Double
let passengers: [Passenger]
let destinations: [String]
}
struct Passenger {
let name: String
let age: Int
}
Next, let's see how we can provide Extra Data mappings for these models:
extension Passenger {
init?(extraData: [String: RawJSON]) {
guard let name = extraData["name"]?.stringValue else { return nil }
guard let age = extraData["age"]?.numberValue else { return nil }
self.name = name
self.age = Int(age)
}
func toExtraData() -> [String: RawJSON] {
[
"name": .string(name),
"age": .number(Double(age))
]
}
}
extension BookingFlight {
init?(extraData: [String: RawJSON]) {
guard let flightNumber = extraData["flightNumber"]?.numberValue else { return nil }
guard let price = extraData["price"]?.numberValue else { return nil }
guard let departureDate = extraData["departureDate"]?.stringValue else { return nil }
guard let arrivalDate = extraData["arrivalDate"]?.stringValue else { return nil }
let destinations = extraData["destinations"]?.stringArrayValue ?? []
let passengers = extraData["passengers"]?.arrayValue?
.compactMap(\.dictionaryValue)
.compactMap(Passenger.init(extraData:))
?? []
self.flightNumber = flightNumber
self.price = price
self.departureDate = StreamDateFormatter.date(from: departureDate)
self.arrivalDate = StreamDateFormatter.date(from: arrivalDate)
self.destinations = destinations
self.passengers = passengers
}
func toExtraData() -> [String: RawJSON] {
[
"flightNumber": .number(flightNumber),
"departureDate": .string(
StreamDateFormatter.dateString(from: departureDate)
),
"arrivalDate": .string(
StreamDateFormatter.dateString(from: arrivalDate)
),
"price": .double(price),
"destinations": .array(destinations.map(RawJSON.string)),
"passengers": .array(
passengers
.map( { $0.toExtraData() })
.map(RawJSON.dictionary)
)
]
}
}
Then, we can extend the ChatMessage model and add a bookingFlight property:
extension ChatMessage {
var bookingFlight: BookingFlight? {
guard let extraData = extraData["flight"]?.dictionaryValue else { return nil }
return BookingFlight(extraData: extraData)
}
}
Finally, if we want to create a message with the booking flight information, we can do it like this:
let bookingFlight: BookingFlight = ...
let extraData: [String: RawJSON] = ["flight": bookingFlight.toExtraData()]
let channelController = client.channelController(for: yourChannelId)
channelController.createNewMessage(text: "A new message", extraData: extraData)