How to manage new Breeze entities which are aggregate roots? - asp.net-web-api

Question

I have a domain model which has a Customer, which in turn has 1 Address (1:1) and 1 or more Phone numers (1:M).
Customer has user supplied PK (a string), while Address and Phone use identity column (server generated).
I am struggling in trying to understand how to manage Breeze entity creation for a "Add new Customer" screen.
The form on the screen allows user to enter Customer, Address, and Phone data.
I am using Durandal and Knockout so my "customeradd.js" viewmodel looks something like this:
// -- snip ---
var customer = ko.observable(),
hasChanges = ko.computed(function () {
return datacontext.hasChanges();
});
var vm = {
hasChanges: hasChanges,
customer: customer,
activate: activate
};
return vm;
function activate() {
customer(datacontext.createCustomer());
}
// -- snip ---
and my "/services/datacontext.js" :
// -- snip ---
breeze.NamingConvention.camelCase.setAsDefault();
var manager = new breeze.EntityManager(config.remoteServiceName);
var hasChanges = ko.observable(false);
manager.hasChangesChanged.subscribe(function (eventArgs) {
hasChanges(eventArgs.hasChanges);
});
function createVehicle() {
return manager.createEntity("Customer");
}
// -- snip ---
My questions are following:
Once I create a Customer, do I need to create Address and list of Phones and add them to Customer entity before making it a KO observable? Or is this done automatically by createEntity() method?
How do I create a Customer but without having to specify the Id? If I set the key to null or '', Breeze complains ("Error: Cannot attach an object to an EntityManager without first setting its key or setting its entityType 'AutoGeneratedKeyType' property to something other than 'None'"). However, if I generate the temp key (using either breeze.core.getUuid() or something else), then it shows up in my Id form field, and I really want the end user to specify it....Do I have to resort to extending the entity with extra field and then do the swapping and validation before saving (I don't like this idea at all)? Is there a better way?
In order to enable/disable buttons on my form I am tracking if there are changes in EntityManager. But every time entity is created, it is automatically in 'added' state so hasChanges is true. What I want is for changes to be picked up only if user edits the form (and therefore makes changes to underlaying entity). What is the best way to approach this?
BTW, I have seen this recommendation to register custom constructor for entity (I have already implemented it but I am still not clear how to let user supply their own id and to flag entity as modified only when user edits it...)

Answer 1

I realize this has been up for a while, but here are my thoughts (in case anyone comes looking).
If you use the entityManager to create your customerl and everything is specified correctly in the metadata, you can just create the customer and add phone numbers/addresses as needed. Breeze automatically makes an entity's properties observable (if specified correctly and if breeze knows that KO is being used)
If you can only do it the way that you say, then you are stuck. Ideally, you would have a user-entered ID which is NOT the key (though you could still force it to be unique) and a database-generated key, which Breeze will manage behind the scenes (assigning a negative key until it is saved to the data store, then updating the key and all related keys without any input from you).
if you use the 2nd approach for answer 2, then your buttons can easily be enabled and disabled using ko data-binding. When you create the entity, save its value to the viewmodel (custSource). Then you can add to the save button the data-bind="disable: custSource == Customer(), enable: custSource != Customer()". (You might need to play around with the syntax -- I haven't tested that part yet)
I don't think you need a custom constructor unless you are doing something different from what I understand.
PS. you should be aware that I believe Breeze wants Knockout defined as 'ko', while Durandal definitely expects it to be 'knockout', so you will probably need a 'map' property in your require.config

Answer 2

I think you could solve some of your problems by taking a slightly different approach to your entity creation. Here's your current approach:
Create a customer entity
User modifies that entity
Save the changes
Instead, try this:
User enters customer information
Create and save the customer entity
I realize that this doesn't really answer your questions, but I've found the second approach to be much easier to implement. Just have the user enter all the information you need to create a customer, and then supply those values to createEntity.
customeradd.js
// -- snip ---
var vm = {
customerId: ko.observable(),
address: ko.observable(""),
phoneNumbers: ko.observableArray([]),
submit: submit
};
return vm;
function submit() {
datacontext.createCustomer(
vm.customerId(),
vm.address(),
vm.phoneNumbers());
}
// -- snip ---
/services/datacontext.js
// -- snip ---
/**
* Creates a new customer.
* #param {int} id - The customer's id number.
* #param {string} address - The customer's address.
* #param {string[]} phoneNumbers - An array of the customer's phone numbers.
*/
function createCustomer(id, address, phoneNumbers) {
return manager.createEntity("Customer",
{
id: id,
address: address,
phoneNumber: phoneNumbers
});
}
// -- snip ---