Multiple controllers manipulating content in an Angular directive? - javascript

I have a problem I haven't come across before, and I'm completely lost as to how to solve it.
I have a container which is used to display success and error messages across a wide variety of views. This container is defined by an Angular directive.
The problem is that I would like to have a service or something similar which I can inject into my controllers. I could then use methods on this service to make the "alert box" appear and/or change in content.
How do I go about achieving this or a similarly DRY setup in Angular?

Three perfectly good methods:
Use angular's event system, rootScope.$broadcast or scope.$emit and scope.$on as listener, see the documentation here: https://docs.angularjs.org/api/ng/type/$rootScope.Scope#$broadcast
https://docs.angularjs.org/api/ng/type/$rootScope.Scope#$emit
https://docs.angularjs.org/api/ng/type/$rootScope.Scope#$on
inject the service into the "alert box" directive, let it register itself somehow with the service, that way the service knows of its existence and can control the directive's controller, or its scope, or the element directly, or whatever logic you wish to use.
Use a container as parent, that has the orchestrating logic. the child directive's can require the container controller, and call functions etc. on the container, one child directive is then able to trigger another child through this orchestrating parent container.
EDIT:
My point wasn't to show you how to do it in the most generic and cleanest way, because I don't know your exact situation, you should always consider how generic and abstracted you want your functionality.
Here is a very very simple example to showcase that it's not about finding some complex system or pattern, but finding something that works well for you
method 2 example:
angular.module('myApp').service( 'myService', myService );
function myService(){
this.alertBoxes = {};
this.registerAlertBox = function(name, handle){
this.alertBoxes[ name ] = handle;
}
this.toggleAlertBox = function(byName){
this.alertBoxes[ byName ]();
}
}
I personally would use method3 from the looks of what kind of functionality you're looking for, method 2 could be a generic pubsub service using rootScope.$broadcast and scope.$on, or not even bothering with those and doing it like a very straight forward pubsub.
method 1 really is the simplest way, but obviously would benefit from being abstracted away into a service, where you inject the service everytime you need a very specific pubsub event.
For an example of a pub/sub pattern: Pub/Sub design pattern angularjs service

Related

Using a service for small task

i been reading about services or factories in angularjs, but im having some trouble finding the best solution, basically i need to pass some data from one controller to another controller, it is a boolean value, but i dont want to create a service for just a small task.
I believe that wouldnt make much sense for just a small job. is there other way in angularjs for this type of situations? Where i could pass small data between controllers. I been looking around in angularjs documentation, but cant figure out the best solution.
Use $rootScope.emit()
in Controller A
$rootScope.emit('toggle',true);
in Controller B
$rootScope.on('toggle', function(value){
})
For tiny items, you could use parameters. The the end user, they'd look like a part of the URL string. This is avaible with and without using ngRoute. Have a look at this stack question.
For more complex data or data that's unsuitable to displaying to an end user, use a service or factory. Seems like overkill, but it gives you greater flexibility.
A $broadcast/$on pattern just gets messy and harder to troubleshoot.
If it's parent/children controller, you can transfer your value with $scope or $emit/$broadcast.
If controllers are on the same level(siblings) you can make wrapper controller for them to store shared data.
If you think there would be similar requirements for other tasks you can consider service, and making it abstract and reusable(some sort of helper).
In any way, you didn't provide enough of info, and there could be a lot of solutions until we see real example.
If your controllers have a child parent relationship (in any level) then you can try with $broadcast or $emmit to throw the data and $on to catch that with a a event. Otherwise inject $rootScope to one of them and trigger either $broadCast on the monitor of $rootScope, or $emmit on the monitor of $scope and catch thet data using $on('eventName', function(ev, data){}) correspondingly.

Angular Project Architecture

I am building an app in angular, which consumes different APIs and Gives options for the user to select it will be recorded and sent back to the server.
I have designed it as follows.
All the common logic in Main Controller and all other options in different controllers as the child of main controller.
Main Controller retrieve all the data that are required to run the app.
which is consumed by all other child controllers.
To make sure data is loaded I am using promise attached to scope. So all the child controller will know data loaded.
I have moved data updation part of all child controllers to main controller
because all the updates happen in one object.
Child Controller emit/broadcast to communicate between child and main. So when update happens child will emit an event with data which will be captured by Main and it will do the update.
MainController {
$scope.loaded = DataService.get();
$scope.userOptions = {};
$scope.$on('update',function(){
updateUserOptions();
})
}
ChildController {
$scope.loaded.then(function(){
//all logic of child controller
}
$scope.onselect = function(){
$scope.$emit('update',data);
}
}
Questions
Is it a good practice to use events between controllers ?
is it good to use promise attached to scope for child controllers ?
Will it improve my code if I start using services ?
I will try to answer your question based on my own experience. Recently I've built a single page application and I've refactored its architecture.
Here are my answers:
Is it a good practice to use events between controllers? IMHO, it is the most flexible way to share information between all controllers even if they have isolated scope (using $broadcast or $emit for example). This is called the Observer design pattern. However, you can use services instead of events to share data between them. If you are going to use $rootScope, be careful as all the $scopes inherit from $rootScope.
is it good to use promise attached to scope for child controllers ? Firstly, you have to learn about how scope inheritance works. You have to take care to avoid property shadow in JS. Secondly, I would move out all the logic from scope.loaded in ChildController to a service such as ChildService. Keeping the business logic (such as request, etc) in Services instead of Controllers, will ensure it can be re-used.
Segregation of business logic is good design principle.
Will it improve my code if I start using services ? I answered this question above.
In addition, in order to build a good architecture I've read this angular style guide written by John Papa.
I recommend the following changes:
To make sure data is loaded I am using promise attached to scope. So all the child controller will know data loaded.. Instead I would emit a custom 'loaded' event in the MainController using $scope.$emit('loaded'). After that, in the ChildController I would use $scope.$on('loaded', function(){}) to handle the event.
I would move the updateUserOptions function to a service and inject the it into just the controllers that need it.
I hope that helps!
Is it a good practice to use events between controllers ? Not as the main form of data sharing, but you can use it to notify about system events, such as data ready.
Is it good to use promise attached to scope for child controllers ? Don't use scope inheritance, it causes lots of annoying problems.
Will it improve my code if I start using services ? Yep.
This is what I would do in your place:
dataService - this service is responsible for all data coming in / going out. Whenever a request for data is made (no matter which controller asked for the data), the service caches the data (save the promise is good enough). All further requests get the cached data unless they specify they want a fresh data. Whenever data is updated (1st time or refresh), the service broadcasts a 'dataReady' event via $rootScope to which the main controller and other subscribers can listen.
The service is also responsible for data updates, and when the data is updated you can also broadcast an event via the $rootScope.
When the event is activated, all subscribers query the service, and get the data they need.
Controllers - avoid controllers, use directives with isolated scope, and pass the data between them using attributes. In this way you can be sure that each directive gets what it needs, and not everything. The directives can communicate using attributes, services, broadcast / emit or require their parents / siblings if they work closely together.
Is it a good practice to use events between controllers ?
No it's not, it will be deprecated by Angular JS 2.0. It also often leads to unmanagable tangle of events which are hard to understand and debug. Use services to share data between controllers. (Inject same service into multiple controllers, service then holds data, controllers bind to that data and are automatically synchronized) I wrote a blog post explaining this use case.
Is it good to use promise attached to scope for child controllers ?
No it's not. Use promises and resolve data in services. Don't use $scope at all but use controllerAs syntax instead. $scope was deprecated also in Angular JS 1.X because it's usage leads to many different problems with scope inheritance.
Will it improve my code if I start using services ?
YES! Use services for all logic and data manipulation. Use controllers only for UI interaction and delegate everything to services. Also use ui-router for managing state of your application.
I'm not going to answer your questions directly as I have some other comments as well. I think the approach you mentioned is not the best way to build angular applications.
All the common logic in Main Controller and all other options in different controllers as the child of main controller.
It's against all angular style guides to place common logic in controllers. Controllers should only be used for the logic related to the view (data binding, validation, ...). Because the code inside a controller is not reusable, the less code you have in a controller the better. The more logic you have in services, the more scalable your application becomes.
Fix: I suggest you create a service that retrieves data from the server, and inject this service in controllers as you need. Notice also this way offers better dependency management as you can keep track of which controllers need which services exactly.
Nested controllers should be avoided when possible, because angular keeps track of all the active scopes and re-evaluates them in every $apply() loop.
Fix: same as #1, use services instead of the main controller.
To make sure data is loaded I am using promise attached to scope. So all the child controller will know data loaded.
Using a promise for data retrieval is a good practice. But, again, keeping it in a service is much cleaner than main controller.
I have moved data updation part of all child controllers to main controller because all the updates happen in one object.
Child Controller emit/broadcast to communicate between child and main. So when update happens child will emit an event with data which will be captured by Main and it will do the update.
Fix: use a service with an update function instead of events. Events are harder to debug and track. And you need to unregister event handlers on destroying a controller. If you can use a function/promise instead of events, then it's usually a better idea.
Is it a good practice to use events between controllers ?
A problem with your current set-up is that you're implicitly relying on the hierarchy of your controllers (the fact that one is the child of the other) - because you emit the event, only scopes higher up on the hierarchy can catch it. Besides being an implicit connection (that a developer has to remember), this also limits he extendability of this feature.
On the other hand, if you injected a shared service into all the controllers that need it, the connection between the controllers would become explicit and documented, and their scopes' position in the hierarchy independent. This will make your architecture easier to maintain, with the added benefit of also being easier to test, for one.
You can still implement an observer pattern with a service.
is it good to use promise attached to scope for child controllers ?
The issue of polluting scopes pointed out in other answers is valid. This is one of the reasons why it's better to limit the number of objects you attach to your scope, and to use objects as bundles of variables on your scope instead of attaching all the variables to the scope directly.
(For an explanation of these reasons, see discussions about "always having a . in your bindings".)
(Of course, don't do this blindly just to reduce the number of variables, try to find semantic connections between variables that might be bundled together sensefully.)
Will it improve my code if I start using services ?
I think the above answers already outline the answer for this: yes. There are other benefits too, but this format is not best for too long answers, so I won't list anything else now.
All in all, these above pointers are not big issues with your code currently, but if you're looking for the best architecture, I think you can do better.
Answers:
No, it will be deprecated soon.
$scope is deprecated already.
Services is a great choice. Services allow us to share data and behaviour across other objects like controllers.

Class methods for models with access to store

I have been battling this issue for a while now.
In my Ember app (using ember-cli) I have a model that I would like to attach some class methods for.
I would like to be able to call from my controllers Model.allWithIssues to find all of the model instances that have registered issues.
To achive that, I have added a method using the following code:
Model.reopenClass({
allWithIssues: function () { ... }
})
My problem is, I don't have access to the data store from inside the model.
I have tried in many different ways inject store:main to the model but with no luck.
One answer here even claimed there is no way to inject to a model, while others suggested ways to achieve DI into models that simply didn't work.
Is my approach completely wrong? Should I keep this logic in a separated class?
EDIT:
The solutions I had in mind are:
Make a generic controller that includes this methods and have all of the controllers that need this method extend it.
Some sort of mixin
Make a "repository" class, working as an abstraction layer between the controllers and the store.
I'm still not sure which route is the best to go in, but all of those seem too robust for something as simple as this.
Controller is not the right place either, unless you have all models loaded, and what you do its a computed propert.
the model's hook in a router would be a better place, its whitin its responsibilities of an adapter to loa data, deserialize it, and provide you with model instances.
Or you can create a service, that lives in you /lib folder, register it with the CI, and inject the store to it. depends on your use case.

EmberJS - Calling components methods from outside with a couple solutions (call for discussion)

The following is from an issue I posted on EmberJS GitHub, but Stack Overflow is better suited for a discussion than GitHub.
I am building a few complex components at the moment including composite components and I hit a roadblock with the extreme isolation components live in.
There are several cases where I don't need the components to trigger an action on a controller, but where a controller needs to trigger a behaviour change on the component.
Problems is that the components don't know about the controller and the controller is not creating the components either: they are defined in a template.
I kind of solved the problem by subclassing the Ember.Component class to offer a way for messages to get through components.
The new component subclass breaks the on purpose isolation of components that shouldn't know about the outer controller.
The 2 less invasive options I found to make component methods calls from outside are:
Cache component / name of instance pairs in a global array like
App.components, then call a component method with
App.components['name'].method()
Trigger events from outside, register and handle them in the
components. However in that case I am passing an eventSource object
to the component, often a controller like so: {{my-component
eventSource=controller}}
My question is about how could we solve this problem in the most elegant and less invasive way possible for components ?
For achieving composite components, using the components like lego pieces, it seems impossible to me at the moment to see how we can achieve that goal without breaking the components isolation.
Any input, ideas, solutions, discussion is very welcome.
Note: By the way, the first method that breaks the component isolation is inspired by the work done on the ember-bootstrap components: https://github.com/ember-addons/bootstrap-for-ember
The author had to solve the same problem of being capable of triggering methods inside the components from outside.
Another note: Just for the record, another way to access a component is to use Ember.View.views['name'] where name is a view name you gave to your component. However I feel dirty to make such calls, even more from a controller.
In general, I would try to solve this by binding properties to your component, which could then change according to computed properties or observers based on those properties.
For instance, instead of trying to call a method like deactivate on a component, bind a property such as active to a property in the template:
{{my-component active=formEnabled}}
I'm hesitant to recommend passing an eventSource to components as a general solution (like your {{my-component eventSource=controller}} example). I imagine this could work with a class or mixin that just emits specific events and is tightly coupled with your component, but I'm struggling to come up with a use case that justifies this approach.

Calling into or between controllers in AngularJS

I have some fairly complicated logic in a bootstrap dialog which I've moved into its own controller for isolation.
There are times I want to launch the dialog or call a function in the controller based on some logic that occurs elsewhere in the app - in another controller, or a service. I've achieved this by adding an id to the ng-controller element then looking up the element by that id, and calling things off the .scope() of that controller. Essentially this:
In html:
<div id="modalController" ng-controller="modalController">
And in another service or controller:
angular.element("#modalController").scope().somefunction()
This seems pretty weird that I can't just get a controller by name. Is there a way to do this?
Create a service and bind the model to data maintained in that service. Make a change to the model within the service and it's made everywhere.
You could also create a service that provides a pubsub interface to the changes you need to make.
Yet another way to do it would be to have a single model representing the state of your system and modify that. Attach the relevant parts of that model to the scopes of each widget as necessary and you have a communication device built in.
It sounds like you are making a change in one place that should cause a change in another place. If that's the case, I'd argue having a service that updates all parts of the model correctly is the best way to go. Always imagine what you'd do if you added another widget that hangs off this functionality.

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