AngularJS - removing the line between SPA and AJAX data binding - ajax

Question

In Angular, speed is the name of the game and rendering views with useful data as quickly as possible is always sought after. Angular allows us to reference data between the Controller and the View seamlessly using Angular's templating engine, which can make rendering views with correctly bound data lightning fast.
For example, lets say we have a simple Angular App which is simply a table of contacts with fields like First Name, Last Name, Phone, Email, and Address. We then want a Details view that appears when you click on a table row. We can wire up the <tr> to change views on click like this
<tr ng-repeat="contact in Contacts" ng-click="showDetails(contact)">
Then we can change the view and "instantly" show contact data in the new view. For example, we can change an <h1> at the top of the page to be Contact - John Smith using the data that was provided in showDetails.
While this data is being shown, more data can be retrieved from the server asynchronously that will then fill in the rest of the fields.
However, what do we do if we want to get to this details page directly from the url? If the contact table was sitting at /contacts and the details page was something like /contacts/detail/1 then attempting to go directly to /contacts/detail/1 would result in the <h1> above to be blank.
This is clearly because we did not use the showDetails() method to invoke the view and pass the clicked contact into it directly. In this case, we would need to take the contact id in the URL and run an AJAX request to get ALL of the data.
My question is, at what point do we draw the line between trying to make our views and data quickly accessible and making them robust?

Answer 1

Robust is a must.
So we need to start there. Then we can move forward to optimize and make data "quickly accessible", as you put it, as much as possible.
In order to do that, every view in an SPA that is directly correlated to a URL needs to be initially stateless. That basically means that a reload on any url will load the desired view correctly and completely.
We can get the best of both worlds by using nested routes. If every route loads only what it needs, but also draws on parent routes (loading them if necessary, or just using them if they have already been provided) then you can achieve both robustness and "quick accessibility" to data.
In your particular example, the base route would be contacts. Then there could be a nested route inside of that which would display the details of a particular contact, contacts/detail/{id}. Loading the base url would load the list of contacts, and loading the details view would load both the list of contacts and the details of a particular contact. To provide quickly accessible data when going to the nested view, we could include logic that checks to see if the parent view data is already loaded, and only load if necessary. Then when navigating from the contacts to the contacts/detail/{id} view, we could quickly display data from the parent view in the child view, while loading data specific to the child view. A reload at contacts/detail/{id} would simply load both. When navigating back to the parent, the parent data would already be loaded.

Answer 2

If you were to use something like ui-router to create complex routes, then you would not use showDetails() to alter the model, you would use showDetails() to alter the route. Then your model would set itself up based on the route, and your view would follow.
For example, you could have something like:
$scope.showDetails = function(contact) {
$state.go('contacts.detail', { contactId: contact.id });
};
Then the controller could use $stateParams to retrieve any data you wanted for the specific contact from the server (asynchronously using promises). You could also include your own flavour of caching/loading via services to manage things like performance if you found it necessary.