RejectChanges() doesn't undo changes when changes are made on a new entity? - angularjs

Question

I have a factory with that returns a new entity:
//myDataFactory
//some other code here...
function create() {
return manager.createEntity(entityName);
}
In my controller, when ever the backend returns a 404 (not found), I simply trigger that create() method when the controller is activated, otherwise I set the object to whatever was returned.
//myDataController
//some other code here...
init();
function init() {
var promises = [
getMyData()
];
console.log('populating MyData');
return q.all(promises).then(function(){
logger.info('populated MyData.');
});
}
function getMyData() {
return myDataFactory.getMyData(true).then(
setMyData,
createNewMyData
);
}
function setMyData(data) {
vm.myData = data[0];
}
function createNewMyData() {
vm.myData = myDataFactory.create();
}
In the UI, I have an undo button, that simply calls this function in the myDataController:
function undo() {
vm.myData.entityAspect.rejectChanges();
vm.termsForm.$setPristine(true);
}
The undo() function above works really well when there is an object returned from the database. But when I try making changes to a newly created entity which isn't saved yet, when I click undo, it's not going back to it's original value. Why? How do I resolve this? Any help would be greatly appreciated. :D
I am using angularjs with breeze btw.

Answer 1

"Original values" are the values that an existing entity had prior to your current, unsaved changes.
A new entity ... one not retrieved from the server and not yet saved ... lacks "original values". It only has "current values". Therefore, rejectChanges has nothing to roll back to.
There are other important differences as well. Look at the thing.entityAspect.entityState.name of a thing entity both before and after calling rejectChanges.
If the state before is "Modified", the state afterward is "Unchanged". But if the state before is "Added", the state afterward is "Detached" ... meaning that the thing is no longer in the EntityManager cache and is ripe for garbage collection.
With these facts in mind, what would you like the behavior to be? Once you know, we can work out a satisfying plan for your scenario.

Answer 2

For those stuck, here is my solution based on what I gathered from Mr. Ward's answer. I used entityState.isAdded() instead.
function undo() {
if (myDataIsNew()) {
resetMyData();
} else {
vm.myData.entityAspect.rejectChanges();
}
setPristineForm();
}
function myDataIsNew() {
// A new entity in cache that does not exist in the backend database
return vm.myData.entityAspect.entityState.isAdded();
}
function resetMyData() {
//clear each property.
}