Concurrent save are not allowed : breeze error

Question

  vm.alterExistingSortOrder = function () {

        $.each(vm.M1010DxCodeSorterListBox2(), function (index1, value1) {


            if (vm.M1010DxCodeSorterListBox2()[index1].IsNewDxCode == false)
            {
                 return datacontext.fetchEntity("EpisodeDxM00Rel", vm.M1010DxCodeSorterListBox2()[index1].Id).then(function (result) {
                    var episodeDxM00RelEntity = result.entity;
                    episodeDxM00RelEntity.SortOrder(index1);
                    vm.save();
                });

            }

        });


        $.each(vm.M1016DxCodeSorterListBox2(), function (index2, value2) {


            if (vm.M1016DxCodeSorterListBox2()[index2].IsNewDxCode == false)
            {
                 return datacontext.fetchEntity("EpisodeDxM00Rel", vm.M1016DxCodeSorterListBox2()[index2].Id).then(function (result) {
                    var episodeDxM00RelEntity = result.entity;
                    episodeDxM00RelEntity.SortOrder(index2);
                    vm.save();
                });

            }

        });
};

I have a function in which I have 8 for loops (in code sample I am just showing 2 loops). I am fetching an entity within that loop, and changing one of its properties. Ideally I want to save all the entities together instead of saving one by one which I am currently doing and that gives me the concurrent save error but I am not sure how can I save all these modified entities together (where should I write a single save method call considering there are multiple promises being returned by the fetchEntity methods)

Answer 1

Breeze does support concurrent saves but you need to explicitly turn this capability on via the SaveOptions class: http://www.breezejs.com/sites/all/apidocs/classes/SaveOptions.html

myEntityManager.saveOptions = new SaveOptions({ allowConcurrentSaves: true });
myEntityManager.saveChanges().then(...);

That said, it probably makes more sense to refactor/rewrite your code so that you can perform a single save with multiple entities. Take a look at the Q.all method (https://github.com/kriskowal/q) to see how to compose a save promise that is performed after ALL of your fetches have been performed.