I am trying to negotiate a conceptual issue in AngularJS.
I have a controller that is currently using multiple services. Among this services, a few are used as a singleton per view. This means that once I enter a certain view (actually state since I am using Ui-Router), these specific services, which have some dependencies among themselves, are singleton(s).
However, when exiting this view and going later going back should instantiate new instances of them (and again being singletons for this state).
There are a few possible solution I came out with, all of them are not great:
Manually force instantiating them every time entering this view.
Manually force deleting from cache every time exiting this view.
Using a controller rather then using service/factory/provider.
Creating my own "factory" type, which will be implementing the angular's injection without being a singleton.
I was wondering if angular can offer some sort of "type" (such as non-singleton factory), that can solve this issue.
Related
I've been reading up a more in depth about angularjs directive and controller, what should be in one and the other. The situation is this, I have multiple people with their types -> policemen, medicine, lawyers ... etc. inside the admin panel app, where the admin can manage them. In one section the admin can create, edit, delete them. The current versions controller does almost all the work: UI (bringing up the right form, hiding the other forms...), and logic (deleting, creating, updating methods for each person type). As I understand this is not good, because the controller does multiple things (no single responsibility). And even further the controller should only bind values to scope.
But does that mean, that I should only pull all the people (inside controller) and pass it some master directive which will manage it all? Or should their be more directives inside directives to divide the responsibility?
And if so, the controller will have to use the same service as the directive/directives. Controller for pulling people from back-end) and the directive/directives (for creating/updating/deleting) is this DRY?
Without code it's hard to give a precise answer, but the general idea when working with angular is this:
Controller: The controller is responsible for keeping the views up to date with all the changes that are happening throughout your app. This means that it should not contain the business logic, this logic should instead be separated into small services. Each handling different parts of the logic for your app.
Service: As stated above, a service should contain your business logic. Meaning that heavy calculations, manipulations etc. should be put into a service. Since services are singletons you can easily inject this service anywhere and re-use the logic within it, something you cannot do if you've put your logic inside a controller.
Directives: Like controllers, directives shouldn't have any business logic in them. Directives are only there to create re-useable functionality as well as giving you a place to handle direct DOM changes. DOM changes should never be done anywhere but from within a directive.
To answer this:
And if so, the controller will have to use the same service as the directive/directives. Controller for pulling people from back-end) and the directive/directives (for creating/updating/deleting) is this DRY?
If you have the data bound to a controller, you should not necessarily need a directive to handle the CRUD operations. Since the data is bound to the controller, you can easily create a template which reacts to the data changes automatically using ng-repeat, ng-if and so on.
So my understanding is that factories are singletons so any stateful data for a session would be ill placed here.
My next point of call was a service which returns a new instance of the service when injected however I am unsure how I would share one instance of the service to multiple controllers.
Is this an accepted way to solve this issue or does angular provide a better way?
My current use case is that I have a view with some partial views (each partial has it's own controller) and a modal window which takes in a row id and will display data dependant on that data.
I need to be able to share a instance of the service (or equivalent) across these controllers but on a per session basis.
How is this best done?
The singleton exists for one user and loaded SPA. Thats what you would usually refer to as a session. Its a good place to store data that needs to be accessed by different controllers.
I am trying to understand singleton pattern.
I write a lot of code in angular and recently I wanted to refactor some of my code and move it to a common place which can be shared by different controllers.So I moved all common utils to my services.
Now the documentation over here says that angular services are singletons but I want to understand the reason behind having singleton pattern here ? Why not have multiple instances of the service object instead of passing references to controllers ?
It all falls in the name "Service". Service, acts like a medium to communicate between controllers or even directives for that matter. Not only for communication, you can add a set of utility functions in your service, which can be used throughout the module/app. This does not need to have multiple instances to serve the purpose. Hence, singleton.
Angular services are the recommended way to exchange data and communicate between controllers. In order therefore to allow this data exchange, services are singleton objects which means that you are guaranteed to have the same service reference between all your controllers.
As an example, imagine that you have an Angular application that displays a list of messages received from another user in the center of the page, as well as the number of received messages or new message notifications in the header. The header and the page content will most probably be under different scopes and be handled by different controllers. In order for these two controllers to have the same view of messages received and be able to display them consistently they will need to use a singleton object holding this information. This object is an Angular service.
I'm new to AngularJS and having a hard time wrapping my head around the conceptual model.
Let's say I want to have an object hierarchy to model a stash repository: Projects contain Repositories contain Tags. Do I create one app, one module and multiple controllers? (Can a module have multiple controllers?) Separate app per object type? Separate module per object type?
All the various data types will be populated by making REST API queries. Read-only for now. Does that change things?
Also, why are they called controllers? They seem to be models. As far as I can tell the controller is actually the AngularJS plumbing.
Here is my rather simple explanation:
A module is just simply a container for all the bits and pieces of your app (services, controllers, directives, filters etc).
Your application may contain different modules - some that you wrote and other third party ones, such as ngGrid for example.
You define a module like this:
var myAppModule = angular.module('myApp', []);
A controller is where the business logic of your application resides. The controller may handle the model, but it is not the model.
The AngularJS documentation for controllers states:
Use controllers to:
Set up the initial state of the $scope object. Add behavior to the
$scope object.
I break up my controllers in to the logical functions that they are supposed to handle. For example, I've written an app to help with combat tracking in a tabletop RPG. I have a controller that handles martial combat and another that handles magick. I also have another controller that helps with the characters. All these controllers are part of my combat app.
I only have one service that is responsible for querying a REST API to retrieve stats and results from a database.
The AngularJS documentation has improved a lot recently and I would recommend reading through it to give you a rough idea of how things work together!
In your example, I'd have a separate controller for each of Projects, Repositories and Tags. I'd have a service to query your datatypes. These would be grouped as part of one module/app.
I have a nontrivial Angular SPA that uses ui-router to manage multiple views, many of which are visible at the same time. I need models to be visible across controllers, so I have services written that allow me to have controllers pull down fresh copies of model data that has been updated.
I apologize in advance for the length of the question, but I will state the problem then state what I have done to address issues I'm sure others in the Angular community have struggled with.
I believe my problem is not understanding the lifecycle of controllers / views, because I get behavior where a controller initializes correctly the first time I go there, but then seems to never run again, even when I navigate to it using something like $state.go("state name").
In one view (contrived example), I show a summary of information about a customer, and in another view I allow a user to update that customer's more detailed profile. I want a user to edit, say, the customer last name in the detailed view, and have the summary view automatically recognize the change and display it.
I have a fiddle that shows 3 views and a simple password changing Service. The flow goes like this:
You can see each view gets initialized and displays the initial password retrieved from the service. All views are in sync with the DataService.
The middle view allows you to enter a new password and change the one stored in the service. Console logging confirms that the service picks up the new password just like you would expect.
(odd behavior #1) When the DataService receives the new password, I would expect the other 2 views (top and bottom) to display the new one. They don't... they still display the initial password.
There is a button to allow a user to go to another state via $state.go("state name") (a child state of the original) which also retrieves the password and displays it. This works the first time (see #5). Now the top view shows the outdated password, the middle view shows the new one, and the bottom one shows the new one as well. This seems normal, since the new view is invoked after the DataService contains a new password value.
(odd behavior #2) If I click back in the middle view and change the password again, and click the button to change states again, the bottom view (which updated just fine in step #4) no longer updates its copy of the password. Now all 3 views show different passwords, even though I am using a single service to pass values between controllers as suggested pretty much everywhere you look for Angular best practices.
Some possible solutions:
Tim Kindberg has an excellent slideshow here that seems to recommend using ui-router's state heirarchy to "pass" data among views that need to pick up values from other views. For a smaller-scale app I think I would settle on this, but I expect our application to have 30+ views displaying data from over 100 REST endpoints. I don't feel comfortable maintaining an application where all the data is being shared by a complex inheiritance tree. Especially using a routing framework that is at version 0.2.8.
I can use events to have controllers listen for changes in the data model. This actually works well. To accommodate performance concerns, I am using $rootScope.emit() and a $scope.$onRootScope('event name') decorator I found on here. With this approach I am less concerned about event performance than I am about wiring this huge app with a bunch of event listeners tying everything together. There is a question about the wisdom of wiring a large app using angular events here.
Using $watch on the value in the DataService? I have not tried this but I am hesitant to hinge an app this size on hundreds of $watches for performances reasons.
A third-party library like bacon.js (or any of a dozen others) that may simplify the event spaghetti, or create observable models that my controllers can watch without the risk of $digestageddon. Of course, if there is a concise way to handle my issue using Angular, I'd prefer not to muddy the app with 3rd party dependencies.
Something that lets controllers actually reference .service modules by reference, so I don't have to depend on tons of event wiring, complex state hierarchies, 3rd party libraries, or seeding the app with hundreds of $watches and then kicking off $digests to update controllers' references to Angular services?
Some solution that relies on time-tested OO and design patterns and not a 3rd-party library or framework that has a version that starts with 0.*.
Thanks in advance... I appreciate the help!
This is no problem of ui.router. If you intend for your model (your data service) to be a single source of truth, you have to refrain from destroying it.. err.. the reference to it that is. And in your case, assigning a primitve (a string) directly to the scope, instead of a reference to it. In other words...
var password = {pw:'initial value'};
and then later setting/binding only on
password.pw = newpassword
{{password.pw}}
Heres a fiddle. And also here is a short little read on scopes, It also includes a video of an angular meetup where Misko talks about "always have(ing) a dot in your model" link and how the $scope is a place to expose your model, not be your model. (aka not a place to assign primitives like password = 'initial value')
Hope this helps!
try remove the animation property of your ion nav view.
remove the property
animation="slide-left-right"
it would be ok.