Swift & DynamoDB

AWS Swift integration is not as straightforward as the sheer size and scope of AWS services might make you believe. After a lot of reading and debugging, I worked out some code that makes this fairly straightforward. This code makes use of ObservableObject which I intend to write about in the near future.


import SwiftUI
import Combine
import AWSDynamoDB

class SessionsData: ObservableObject {
    
    let didChange = PassthroughSubject< SessionsData, Never >()
    @Published var data: [Sessions] = [] {
        didSet {
            didChange.send(self)
        }
    }
    
    init() {
        load()
    }
    
    func load() {
        let dynamoDBObjectMapper = AWSDynamoDBObjectMapper.default()
        let scanExpression = AWSDynamoDBScanExpression()
        scanExpression.limit = 20
        
        var temp : [Sessions] = []

        dynamoDBObjectMapper.scan(Sessions.self, expression: scanExpression)
                            .continueWith(block: { (task:AWSTask< AWSDynamoDBPaginatedOutput >!) -> Any? in
            if let error = task.error as NSError? {
                 print("The request failed. Error: \(error)")
             } else if let paginatedOutput = task.result {
                for session in paginatedOutput.items as! [Sessions] {
                    temp.append(session)
                }
                DispatchQueue.main.async {
                    self.data = temp
                    self.didChange.send(self)
                }
             }
            return true
         })
    }
}

The above class defines an obect that conforms to ObservableObject, a protocol that allows SwiftUI to monitor events on an object and automatically redraw itself on the occurrence of those events. This allows a more obvious separation of the data model and view in Apple's new Protocol Oriented Design Framework.


import SwiftUI
import AWSCore
import AWSDynamoDB

struct Events: View {
    
    @ObservedObject var sessionsData = SessionsData()
    
    var body: some View {
        ...
    }
    
}

The above code is all a person needs to get started implementing their own ObservedObject protocols and get the data model behind AWS moving!