Add support for transforming Messages, Channels and Members

[nuno-vieira]

🔗 Issue Links

Resolves https://linear.app/stream/issue/IOS-638

🎯 Goal

Add support for transforming Messages, Channels and Members. This will allow changing some of the data of these models at run time.

The most common use case for this feature is to easily allow E2EE encryption.

Note

Our Members and User models are different, and since Member is a subclass of User (Tech Debt), transforming Users would not reflect on Members, so at the moment we only provide transforming members. If in the future Users is needed, it needs to be a new function to transform Users.

📝 Summary

A new StreamModelsTransformer protocol is added and can be implemented by customers. Currently, only Channels, Messages and Channel Members are transformable, with limited data that can be changed.

Example usage:

class CustomStreamModelsTransformer: StreamModelsTransformer {
    func transform(channel: ChatChannel) -> ChatChannel {
        channel.replacing(
            name: "Hey!",
            imageURL: channel.imageURL,
            extraData: channel.extraData
        )
    }

    func transform(message: ChatMessage) -> ChatMessage {
        message.replacing(
            text: "Yo",
            extraData: message.extraData,
            attachments: message.allAttachments
        )
    }

    func transform(newMessageInfo: NewMessageTransformableInfo) -> NewMessageTransformableInfo {
        newMessageInfo.replacing(
            text: "Changed",
            attachments: newMessageInfo.attachments,
            extraData: newMessageInfo.extraData
        )
    }
    
    func transform(member: ChatChannelMember) -> ChatChannelMember {
        member.replacing(
            name: "\(member.name ?? member.id)",
            imageURL: member.imageURL,
            userExtraData: member.extraData,
            memberExtraData: member.memberExtraData
        )
    }
}

With the replacing function, if customers want to only change the data of a specific controller, they can do it like so:

let transformedChannels = controller.channels.map {
    $0.replacing(name: "YO", imageURL: $0.imageURL, extraData: $0.extraData)
}

// with combine:
controller.observableObject
      .channels
      .publisher
      .map {
         $0.replacing(name: "YO", imageURL: $0.imageURL, extraData: $0.extraData)
      }
      .sink(receiveValue: { transformedChannel in
         print(transformedChannel)
      })

🛠 Implementation

The way it works is that when asModel() transformation happens, we provide a way to change it before returning the final model.

🧪 Manual Testing Notes

N/A

☑️ Contributor Checklist

• I have signed the Stream CLA (required)
• This change should be manually QAed
• Changelog is updated with client-facing changes
• Changelog is updated with new localization keys
• New code is covered by unit tests
• Documentation has been updated in the docs-content repo

[Stream-SDK-Bot]

SDK Size

title	develop	branch	diff	status
StreamChat	7.0 MB	7.0 MB	+1 KB	🟢
StreamChatUI	4.77 MB	4.77 MB	0 KB	🟢

[github-actions]

	1 Warning
⚠️	Big PR

Generated by 🚫 Danger

[laevandus]

StateLayer needs also this.

[nuno-vieira]

@laevandus I've add it to the state layer already 🤔

[martinmitrevski]

Looks great, I like this approach more! Few more finishing touches (docs, tests) and we're good to 🚢

[Stream-SDK-Bot]

SDK Performance

target	metric	benchmark	branch	performance	status
MessageList	Hitches total duration	10 ms	5.01 ms	49.9% 🔼	🟢
	Duration	2.6 s	2.55 s	1.92% 🔼	🟢
	Hitch time ratio	4 ms per s	1.96 ms per s	51.0% 🔼	🟢
	Frame rate	75 fps	78.32 fps	4.43% 🔼	🟢
	Number of hitches	1	0.4	60.0% 🔼	🟢

[Stream-SDK-Bot]

SDK Size

title	develop	branch	diff	status
StreamChat	7.0 MB	7.0 MB	+1 KB	🟢
StreamChatUI	4.77 MB	4.77 MB	0 KB	🟢

[sonarqubecloud]

Quality Gate passed

Issues
176 New issues
0 Accepted issues

Measures
0 Security Hotspots
84.1% Coverage on New Code
0.1% Duplication on New Code

See analysis details on SonarQube Cloud