Decoder for Atlas Functions result

[solkpolk]

Problem

Decoding results from Atlas App Functions. I'm assuming a lot of people using atlas app functions would like this feature

Solution

No response

Alternatives

No response

How important is this improvement for you?

Would be a major improvement

Feature would mainly be used with

Atlas App Services: Auth or Functions etc

[nirinchev]

Hey, we've been chatting with the team on how to approach this. In the meantime, you could implement your own functions client and use the SwiftBSON library to encode and decode the request and response. I'm not a swift developer, but I threw together some code that should help you get started:

import RealmSwift
import Realm
import SwiftBSON

struct FunctionClient {
    let functionsUrl: URL
    let user: User
    let _decoder = ExtendedJSONDecoder()
    let _encoder = ExtendedJSONEncoder()
    
    init(appId: String, app: App, user: User) {
        functionsUrl = URL(string: "\(app.configuration.baseURL!)/api/client/v2.0/app/\(appId)/functions/call")!
        self.user = user
    }
    
    func callFunction<T: Decodable>(_: T.Type, name: String, args: [Encodable]) async throws -> T {
        var request = URLRequest(url: functionsUrl)
        request.setValue( "Bearer \(user.accessToken!)", forHTTPHeaderField: "Authorization")
        request.setValue("application/json", forHTTPHeaderField: "Content-Type")
        request.httpMethod = "POST"
        
        let serializedArgs = try args.map {
            return try String(decoding: _encoder.encode($0), as: UTF8.self)
        }.joined(separator: ",")
        
        let body = "{ \"name\": \"\(name)\", \"arguments\": [\(serializedArgs)] }"
        
        request.httpBody = Data(body.utf8)
        
        let (data, response) = try await URLSession.shared.data(for: request)
        if let httpResponse = response as? HTTPURLResponse {
            if httpResponse.statusCode == 401 {
                try await user.refreshCustomData()
                return try await callFunction(T.self, name: name, args: args)
            }
        }

        return try _decoder.decode(T.self, from: data)
    }
}

And you use it like:

// Define your strongly-typed model representing the result
struct FunctionResult: Codable, Equatable {
    let result: Int32
}

let functionClient = FunctionClient(appId: "my-app-id", app: app, user: user)
let result = try await functionClient.callFunction(FunctionResult.self, name: "addNumbers", args: [1, 2])

It's not the most elegant solution and the code can certainly be made more swift-y, but I hope it'll unblock you until we have a proper first-party API.

[solkpolk]

Nice idea!
I tried running it but discovered app.configuration.baseURL doesn't exist. Is there another way to obtain the baseURL?

[jsflax]

@solkpolk I opened up a draft for you: #8142

import SwiftBSON

private struct Preferences: Codable {
     let favoriteColor: String
     let apples: Int
}

func testUserCallFunctionAsyncAwaitCodable() async throws {
    let user = try await self.app.login(credentials: basicCredentials())
    let preferences = try ExtendedJSONDecoder().decode(Preferences.self,
                                                       from: try await user.functions.preferences())

    XCTAssertEqual(preferences.favoriteColor, "green")
    XCTAssertEqual(preferences.apples, 10)
}

Using my branch, you should be able to use the normal pathway (user.functions.(...)) with an overloaded return of Data, which you can then hook into the ExtendedJSONDecoder from SwiftBSON. We'll look into more permanent solutions in the near future.

[solkpolk]

Works. Many thanks 🙏