Not sure how to add record if not exists jaydata sqllite

Question

I am trying to accomplish the following task. I have a json array returned from a remote database and I want to iterate over it, check if a record with the ID of the object exists in the local database. If exists, I want to update the record, if it doesn't I want to attach it. The code is goes as follows:

$.each(data, function(idx, task) { 
                        var taskToUpdate = $org.context.Task.attachOrGet({ Id:task.TaskId});                        
                        taskToUpdate.TaskType = task.TaskType;
                        taskToUpdate.StatusId = task.TaskStatusId;
                        taskToUpdate.TaskStatus = task.TaskStatus;
                        taskToUpdate.DateScheduled = task.Date;
                        taskToUpdate.TimeSlot = task.Time;
                        taskToUpdate.LastUpdated = new Date();
                        taskToUpdate.TaskName = "Job " + task.TaskId + " " + task.TaskType + " @" + task.AddressOfTask + ", " + task.PropertyPostCode;
                        taskToUpdate.SpecialInstructions = task.SpecialInstructions;
                        taskToUpdate.PropertyAddress = task.AddressOfTask;
                        taskToUpdate.PropertyPostCode = task.PropertyPostCode;
                        taskToUpdate.PropertyType = task.PropertyType;
                        taskToUpdate.NumberOfBedrooms = task.NumberOfBedrooms;
                        taskToUpdate.HasGarage = task.HasGarage;
                        taskToUpdate.HasOutHouse = task.HasOutHouse;


                    });

                    $org.context.saveChanges({
                        success: function(db) {
                            that.messages.push("Tasks saved to local device.");
                        }, error: function(err) {
                            console.log(err);
                            that.messages.push("Errors saving tasks: " + err);
                            navigator.notification.alert("Error saving local tasks to your device!",
                                                         function () {
                                                         }, "Error", 'OK');
                        }
                    });  

The code executes successfully but no records are added to the task table.

Am I missing something?

Answer 1

I went with this code, which seems to work but just doesn't feel "right". Namely the way I detect whether or not the updates have finished to avoid calling context.savechanges() more than one. Please feel free to improve my answer!

function downloadTasksFromWeb(viewModel){
    $org.context.UserSetting.first().then(function (userSetting) {
                viewModel.set("currentUserSettings", userSetting);          

                backofficeUrl = viewModel.get("currentUserSettings.BackOfficeUrl") + "/api/tasks";
                var operatorId = viewModel.get("currentUserSettings.OperatorId");

                var rowsToProcess = 0, rowsProcessed = 0;

                viewModel.messages.push("Connecting to server.");
                showNotificationInfo("Connecting to server.");

                jQuery.ajax({
                    type: "GET",
                    url: backofficeUrl,
                    dataType: 'json',
                    async: false,
                    username: "user",
                    password: "pw",
                    data: {"operatorId": operatorId},
                    success: function (data) {
                        viewModel.messages.push("Tasks received, saving to local device.");
                        showNotificationInfo("Tasks received, saving to local device.");
                        rowsToProcess = data.length;
                        $.each(data, function(idx, task) { 
                            var existingTasks = $org.context.Task.filter("Id", "==", task.TaskId).toArray();

                            existingTasks.then(function(result) {
                                var taskToUpdate = $org.context.Task.attachOrGet({ Id:task.TaskId});

                                taskToUpdate.TaskType = task.TaskType;
                                taskToUpdate.StatusId = task.TaskStatusId;
                                taskToUpdate.TaskStatus = task.TaskStatus;
                                taskToUpdate.DateScheduled = task.Date;
                                taskToUpdate.TimeSlot = task.Time;
                                taskToUpdate.LastUpdated = new Date();
                                taskToUpdate.TaskName = "Job " + task.TaskId + " " + task.TaskType + " @" + task.AddressOfTask + ", " + task.PropertyPostCode;
                                taskToUpdate.SpecialInstructions = task.SpecialInstructions;
                                taskToUpdate.PropertyAddress = task.AddressOfTask;
                                taskToUpdate.PropertyPostCode = task.PropertyPostCode;
                                taskToUpdate.PropertyType = task.PropertyType;
                                taskToUpdate.NumberOfBedrooms = task.NumberOfBedrooms;
                                taskToUpdate.HasGarage = task.HasGarage;
                                taskToUpdate.HasOutHouse = task.HasOutHouse;

                                if (result.length == 0) {
                                    $org.context.Task.add(taskToUpdate);
                                }

                                rowsProcessed++;

                                if (rowsProcessed == rowsToProcess) {
                                    $org.context.saveChanges({
                                        success: function(db) {
                                            viewModel.messages.push("Tasks saved to local device.");
                                            showNotificationInfo("Tasks saved to local device.");
                                        }, error: function(err) {
                                            console.log(err);
                                            viewModel.messages.push("Errors saving tasks: " + err);
                                            showNotificationError("Errors saving tasks: " + err);                                            
                                        }
                                    });  
                                }
                            });
                        });
                    }
                }).fail(function(resultData) {
                    showNotificationError("There was an error communicating with the server.  Please check your settings and try again.");

                });
            });
} 

Answer 2

Instead of the $.each you need a recursive function with the following algorithm: - check if there is any record saved to the local DB with the particular ID

• if yes
  • attach
  • set the properties
• if no
  • create a new typed element entity
  • set the properties
  • add the entity to the collection - context.Tasks.add(newEntity)
• after all your code finished, call context.saveChanges() to persist all the changes in a batch. This is much faster and safe than your code that calls the saveChanes() inside the foreach.

The recursive function is necessary because of the async behavior.