worker.kt

   class SampleWorker(context: Context, workParameters: WorkerParameters) : OffixWorker(context, workParameters) {

    override fun doWork(): Result {
       /*
        getListOfMutations() returns the list of mutations stored in database in the library.
        It's present in the parent class, i.e OffixWorker.
        */
        val listOfMutations = getListOfMutations()

        //get the mutation one by one from list
        listOfMutations.forEach { storedmutation ->

         /*
         Create an object of Mutation<D,T,V> from the stored mutation in the database.
         */
         val obj = getMutation(storedmutation)

         /* Make an apollo client which takes in mutation object and makes a call to server.
         */
         val customClient = apolloClient.mutate(obj)

         customClient?.enqueue(object : ApolloCall.Callback<Operation.Data>() {
              override fun onFailure(e: ApolloException) {
                  e.printStackTrace()
              }

         /*
          On getting a successful response back from the server, delete mutation from the database.
         */
         override fun onResponse(response: Response<Operation.Data>) {
         // Do your work and delete that mutation by calling the deleteMutation() function.
            deleteMutation(storedmutation)
         }
     })
   }
  return Result.success()
}