While Adding New Entity, Identity value is not generated - breeze

Question

I am running into problem, where i extend the Entity to expose hasValidationError. Without that it works fine. Also i found that if I supply the ID before adding the entity it works fine as well. Why is the ID field not auto generating once the entity is extended on the client.
I am now using little different version of the code(i find it more intuitive to extend the entity this way), but it still errors out in the same way.
var Country = function () {
console.log("Country initialized");
var self = this;
self.Country_ID = ko.observable("");
self.Country_Code = ko.observable("");
self.Country_Name = ko.observable().extend({
validation: {
validator: function (val, someOtherVal) {
return false;//val === someOtherVal;
},
message: 'Invalid Value!',
params: 5
}
});
var prop = ko.observable(false);
var onChange = function () {
var hasError = self.entityAspect.getValidationErrors().length > 0;
if (prop() === hasError) {
// collection changed even though entity net error state is unchanged
prop.valueHasMutated(); // force notification
} else {
prop(hasError); // change the value and notify
}
};
// observable property is wired up; now add it to the entity
self.hasValidationErrors = prop;
//dummy property to wireup event
//should not be used for any other purpose
self.hasError = ko.computed(
{
read: function () {
self.entityAspect // ... and when errors collection changes
.validationErrorsChanged.subscribe(onChange);
},
// required because entityAspect property will not be available till Query
// return some data
deferEvaluation: true
});
self.fullName = ko.computed(
function () {
return self.Country_Code() + " --- " + self.Country_Name();
});
};
store.registerEntityTypeCtor("Country", Country);
and then in the button click i am using the following code to create new entity.
var countryType = manager.metadataStore.getEntityType("Country");
var newCountry = countryType.createEntity();
//newCountry.Country_ID(200); //if i add this line no errors occurs
newCountry.Country_Code("India");
self.list.push(newCountry);
manager.addEntity(newCountry); // validation error occurs right after this line
self.selectedItem(newCountry);
self.list.valueHasMutated();

Answer 1

Entities will only get their own autogenerated key if the metadata for their type specifies that this is supported. i.e.
if (myEntityType.autoGeneratedKeyType === AutoGeneratedKeyType.Identity)
This setting means that the key property of the entity is automatically generated by the server, typically for an 'Identity' column on your database.
or
if (myEntityType.autoGeneratedKeyType === AutoGeneratedKeyType.KeyGenerated)
This setting means that you have a server side KeyGenerator that can generate the key for you.
By default, however, myEntityType.autoGeneratedKeyType will equal AutoGeneratedKeyType.None.
In either of the other two cases, breeze will generate a temporary key on the client and then fix it up after a save completes with a 'real' key generated on the server.
If you do not need this capability, then simply create your own ctor for your type that generates a unique key and set it there. see MetadataStore.registerEntityTypeCtor for more details on how to register your ctor.
We are planning on improving our documentation in this area but haven't yet gotten there. I hope this helps.

Answer 2

Perhaps there is nothing wrong at all. How do you know that the id generation is failing? Is it a negative number after adding the newCountry to the manager? It should be.
What is the validation error that you are getting? Does it relate to Country_ID? Perhaps you have a validation constraint (e.g., minimum value) on Country_ID?
The addhasValidationErrorsProperty entity initializer works as intended. I just added a teaching test to the DocCode sample (see "Can create employee after registering addhasValidationErrorsProperty initializer" in entityExtensionTests.js). We haven't deployed it as I write this but you can get it from GitHub.
It follows your example as best I can with the Northwind Employee entity which has an identity id (Employee_ID). The test shows adding the initializer that I wrote in the previous post (not as you may have rewritten it). It shows that the new Employee's id is zero before adding to the manager and becomes -1 after adding to the manager. The -1 is the temporary id of the new employee; it receives a permanent value after save.
The default validationOptions of an EntityManager are set so to validate an entity when it is attached (or added) to the manager. You can change that behavior to suit your needs.
The new employee is in an invalid state when created; it lacks the required First and Last name values (the test displays these errors). Therefore the hasValidationErrors observable becomes true after adding the new employee to the manager and the hasValidationErrors observable raises a change notification that a Knockout UI would hear; these test shows these two points.