不确定如何添加记录如果不存在jaydata sqlite

Question

我正在尝试完成以下任务。我有一个从远程数据库返回的json数组，我想迭代它，检查本地数据库中是否存在具有该对象ID的记录。如果存在，我想更新记录，如果不存在我想要附加它。代码如下：

$.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');
                        }
                    });  

代码执行成功，但没有记录添加到任务表中。

我错过了什么吗？

Answer 1

我使用了这段代码，这似乎有效，但感觉并不“正确”。即我检测更新是否已完成的方式，以避免调用context.savechanges（）多个。请随时改进我的答案！

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

使用以下算法，您需要一个递归函数，而不是$ .each： - 检查是否有任何记录保存到具有特定ID的本地DB

• 如果是的话
  • 附
  • 设置属性
• 如果没有
  • 创建一个新的类型化元素实体
  • 设置属性
  • 将实体添加到集合中 - c ontext.Tasks.add(newEntity)
• 所有代码完成后，调用context.saveChanges(）以保留批量中的所有更改。这比调用foreach中的saveChanes（）的代码快得多，也更安全。

由于异步行为，递归函数是必需的。