Ember.js: Where is the "start" button? - ember.js

I'm used to thinking about a single-page application startup happening like this: 1. Bootstrap some data into critical models, 2. Instantiate a master controller, and 3. Call it's render() method to kick things off.
How is this accomplished with Ember? Following the (meager, sigh) examples in the documentation, it seems like things sort of kick off on their own when the page loads -- templates are compiled, views render like magic when the page loads. I feel like I am missing something fundamental. It there an example online of a more complex app, say something with tabbed or dynamically loaded views?
Lightbulb, going off it is not.

I've started a blog series about getting up and running with Ember on Rails. Here's Part 1:
http://www.cerebris.com/blog/2012/01/24/beginning-ember-js-on-rails-part-1/
I hope you'll find it useful, even if you're not planning to use Ember with Rails. Most of the interesting details are client-side and thus server-independent. The posts so far cover creating an Ember.Application object, loading data dynamically through a REST interface, and then rendering an Ember view on a page in handlebars. I hope it's enough to get you started.

When you extend an ember Application object you can provide a ready function which will be called when the application starts. You have to make sure to call this._super() or else it will break your application. Check out my sample sproucore 2.0 application (ember is the new name of sproutcore 2.0).
The way that ember works is that it sets up a run loop which responds to events. Whenever an event fires, the run loop basically calls the necessary handlers and runs any bindings that need to be updated. Since everything typically happens in the run loop you often don't really write any code to update things. Instead you write bindings which are fired when needed.

Another thing I've done is use an Em.StateManager to bootstrap.
App.Loader = Em.StateManager.create({
start: Em.State.create({
enter: function(mgmt, ctx) {
// this code will execute right away, automatically
}
})
});
Since you use create instead of extend, the object will be instantiated immediately. If you define a state called start, it will be recognized as the default initial state (or you can specify another one by name). So the new StateManager object will immediately enter the initial state, and when the StateManager enters a new state, it will always look for a method of that state called enter and fire it if present.
A state manager is the natural place to initialize your app because the object provides ways for you to micromanage execution order during an async loading process without entangling yourself in too many callbacks.

Related

Flutter unit testing - unable to pump full widget tree

I am just getting started with unit testing in Flutter, and I have hit a bit of a wall. I have a fairly simple app located here:
https://github.com/chuckntaylor/kwjs_flutter_demo
The app is essentially a list view of events where you can tap on one to read more details about the event.
I have two screens for this: events_screen.dart for the list view, and event_screen.dart for the details. I have been trying to write my tests in events_screen_test.dart
My testing difficulties are with the events screen (the list view). After running await tester.pumpWidget(MaterialApp(home: EventsScreen()) I can use find.text('Events') for example to find the title in the AppBar, but I cannot find any of the elements that make up the list.
To clarify further. I am using get_it as a serviceLocator to get the viewModel for the EventsScreen when it loads. The viewModel is the ChangeNotifierProvider, and EventsScreen contains a Consumer to update the list. in EventsScreen initState(), it calls loadEvents() on the viewModel. After loadEvents() is done, the viewModel calls notifyListeners(), so that EventsScreen can update.
How do I ensure that all these steps occur so that I can properly test if the EventsScreen is rendering properly?
I could be approaching this all wrong, so any advice is appreciated.
I have solved my problem, but perhaps someone can shed some light on this. In the end I executed:
await tester.pumpWidget(MaterialApp(home: EventsScreen(),));
// followed immediately by this second pump without arguments
await tester.pump();
At this point, the Widget tree was complete and I could create Finders as I hoped and could run all my expect statements without issue.
I am not sure exactly why this works though.
As you saw calling tester.pump(), after tester.pumpWidget(), do the job. This works for the following reason: you wrote you are using a Provider, and you run a notifyListener after the data are fetched. Now in a normal application run, you see the widget rebuild since you are using a consumer to that provider. In the test environment, this does not occur if you don't explicitly call a "time advance". You can do it calling await tester.pump() (as you did) and this asks to run a new frame on screen, so now you have your list rendered.

unit testing in redux

So the docs suggest using a mock store, but it's just recording all the actions and is not connected to any reducer. I basically just want to unit a test a component, and see that given an action has been dispatched, it changed- something like(in the most general way to describe):
expect(counter.props).to.equal(1)
dispatch(increment())
expect(counter.props).to.equal(2)
any ideas? thanks
There's a couple factors involved here.
First, even in normal rendering and usage, dispatching an action does not immediately update a component's props. The wrapper components generated by connect are immediately notified after the action is dispatched, but the actual re-rendering of the wrapped component generally gets batched up and queued by React. So, dispatching an action on one line will not be reflected in the props on the next line.
Second, ideally the "plain" component shouldn't actually know anything about Redux itself. It just knows that it's getting some data as props, and when an event like a button click occurs, calls some function it was given as a prop. So, testing the component should be independent from testing anything Redux-related.
If it helps, I have a whole bunch of articles on React and Redux-related testing as part of my React/Redux links list. Some of those articles might help give you some ideas.

Ember 1.12.0 instance initializer: deferReadiness method doesn't exist

In ember's blog post about 1.12 release, mentions an example using application.deferReadiness inside an instance initializer. However, it doesn't seem to be working. The first parameter to the initialize function doesn't have a deferReadiness method. Any ideas?
I think it's reasonable to post #tomdale explanation here as an answer.
#tomdale: "It's not possible to defer app readiness in an instance initializer, since by definition instance initializers are only run after the app has finished booting.
Sidebar on the semantics of application booting: "App readiness" (as in, deferReadiness() and advanceReadiness()) refers to whether all of the code for the application has loaded. Once all of the code has loaded, a new instance is created, which is your application.
To restate, the lifecycle of an Ember application running in the browser is:
Ember loads.
You create an Ember.Application instance global (e.g.
App).
At this point, none of your classes have been loaded yet.
As your JavaScript file is evaluated, you register classes on the
application (e.g. App.MyController = Ember.Controller.extend(…);)
Ember waits for DOM ready to ensure that all of your JavaScript
included via <script> tags has loaded.
Initializers are run.
If you need to lazily load code or wait for additional setup, you can call deferReadiness().
Once everything is loaded, you can call advanceReadiness().
At this point, we say that the Application is
ready; in other words, we have told Ember that all of the classes
(components, routes, controllers, etc.) that make up the app are
loaded.
A new instance of the application is created, and instance
initializers are run.
Routing starts and the UI is rendered to the
screen.
If you want to delay showing the UI because there is some runtime setup you need to do (for example, you want to open a WebSocket before the app starts running), the correct solution is to use the beforeModel/model/afterModel hooks in the ApplicationRoute. All of these hooks allow you to return a promise that will prevent child routes from being evaluated until they resolve.
Using deferReadiness() in an initializer is an unfortunate hack that many people have come to rely on. I call it a hack because, unlike the model promise chain in the router, it breaks things like error and loading substates. By blocking rendering in initializers, IMO you are creating a worse experience for users because they will not see a loading or error substate if the promise is slow or rejects, and most of the code I've seen doesn't have any error handling code at all. This leads to apps that can break with just a blank white screen and no indication to the user that something bad has happened."
See also discussion: https://github.com/emberjs/ember.js/issues/11247

Application never routes when model fails to load

I understand that ember-data is still in a fairly unstable state. I just would like to confirm that what I'm experiencing is expected behavior or a bug. And hopefully find some manner of work around.
I have an application that functions correctly in every expected way except one. Best I can tell I've traced it back to way the application routes on initial load. If I start the application from a route #/posts or #/post/1 where the id is valid it works fine. Application starts, routes, and loads the model. Any valid route works fine. If I were to use a route with a bad id #/post/1a534b where ember-data will not be able to find an underlying model with that id, the application never routes.
I've enabled LOG_TRANSITIONS on my application and confirmed it never transitions to a route, doesn't error on routing, never even injects my application template into the DOM. This problem is unique to initial load as it seems to wait for the model to load before injecting. This never happens because the promised model doesn't exist.
So is this expected behavior or is something else at play here?
I will say that my application isn't loaded til after dom ready and is pulled down async on dom ready. This shouldn't make a difference as the application runs fine when loaded with a proper route.
In the mean time I'll see if I can get a jsfiddle as an example since I can't use my code directly.
Unfortunately I believe this is expected behavior at the moment:
https://github.com/emberjs/ember.js/issues/1454
I think there is work being done to address errors and the router in general here:
https://github.com/emberjs/ember.js/pull/2740
In the route, transition to another route if the model fails to load.
model(params) {
return this.store.findRecord('account', params.account_id)
.catch(()=>{
this.transitionTo('admin.accounts');
});
},
I'm currently building an app with Ember 2.10.0

Calling a function after another function is called

I'm programming a controller for use with Ableton Live 8 using the Python-based API. In my code I use a method provided in the API to watch for changes in a property's value, and call a function whenever the value changes. My goal is to change the color of the clip when the value change is noticed.
I have my code completed, and it compiles without error. From Ableton's log:
742234 ms. RemoteScriptError: RuntimeError
742234 ms. RemoteScriptError: :
742234 ms. RemoteScriptError: Changes cannot be triggered by notifications
742234 ms. RemoteScriptError:
It appears this is the result of using the built-in notification system to make a change to the live set during notification. Triggering the actual change AFTER the listening function has finished executing should work. Is this possible using Python?
Edit for clarification:
currently we have
value change noticed, function called
function attempts to change the clips color (results in error)
we need
listener notices value change, function called
function finds the new color value
function execution ends
another function is called outside the listener's scope, and changes the clips color
I did a lot in M4L and know this error by heart :)
I'm afraid you can't do anything about that - to my noob eyes it looks like a built-in security mechanism so you can't loop (Something changed? Change it! Something changed...).
In M4L i used Javascript Tasks to separate the steps (Tasks forget nearly everything),
something like
Observer -> Something changed
Create a Task that reacts
task.execute() or task.schedule(time)
Maybe the python threading module can achieve something similar?
BTW, if you happen to understand anything about the _Framework-Tasks, let me know.
I was having the same issue trying to delete a track from a clip stop listener, then I found this thread and followed #user2323980 suggestion.
There seems to be a "_tasks" object on every Framework class (I found it throught log_message inside ClipSlotComponent and ControlSurface) that handles concurrency between tasks. And it's really simple to use it:
self._tasks.add(Task.run(func, args))
I found some uses of it on Push and MK2 scripts, those are good references.