Searched entire Internet but couldn’t find the modern solution for my problem.
I want to use NSObjectController in pair with Core Data through Cocoa Bindings and struggle to set it up properly. Worth noting that I’m using latest version of Xcode and Swift.
What I’ve done:
For testing purposes I’ve done the following:
Created an macOS app with “Use Core Data” option selected (the app is not document based);
Dragged 2 NSTextFields into the Storyboard Dragged NSObjectController to the view controller scene;
Added Employee Entity to Core Data model with 2 attributes “name” and “surname”;
Done everything from the answer in How do I bind my Array Controller to my core data model?
Set NSObjectController to entity mode and typed in “Employee”,
Prepares Content selected, Use Lazy Fetching selected so all three options checked;
Binded the NSObjectController’s Managed Object Context in bindings inspector to the View Controller’s managedObjectContext;
Binded NSTextFields as follows: Value - Object Controller, Controller key - selection, Model Key Path - name (for 1st text field) and surname (for 2nd).
That’s it.
First set of questions: What I did wrong and how to fix it if it’s not completely wrong approach?
I’ve read in some post on stackoverflow that doing it that way allows automatic saving and fetching from Core Data model. That’s why I assumed it should work.
So here is a Second set of questions:
Is it true?
If it is then why text fields are not filled when view is displayed?
If it is not then how to achieve it if possible (trying to write as less code as possible)?
Third question: If I used approach that is completely wrong would someone help me to connect Core Data and NSObjectController using Cocoa bindings and show me the way of doing so with as less code written as possible using the right approach?
Taking into account that there no fresh posts about this topic in the wilds I think the right answer could help a lot of people that are developing a macOS app.
Thanks in advance!
I think your basic approach is correct, although it is important to understand that you need a real object, an instance, in order for it to work.
Creating a NSManagedObject subclass is generally desirable, and is almost always done in a real project, so you can define and use properties. You can do it easily nowadays by selecting the data model in Xcode's Project Navigator and clicking in the menu: Editor > Create NSManagedObject Subclass…. Technically it is not necessary, and in a demo or proof-of-concept, you often muddle through with NSManagedObject.
Assuming you are using the Xcode project template as you described, wherein AppDelegate has a property managedObjectContext, the following function in your AppDelegate class will maintain, creating when necessary, and return, what I call a singular object – an object of a particular entity, in this case Employee, which your app requires there to be one and only one of in the store.
#discardableResult func singularEmployee() -> NSManagedObject? {
var singularEmployee: NSManagedObject? = nil
let fetchRequest: NSFetchRequest<NSManagedObject> = NSFetchRequest(entityName: "Employee")
let objects = try? self.managedObjectContext.fetch(fetchRequest)
singularEmployee = objects?.first
if singularEmployee == nil {
singularEmployee = NSEntityDescription.insertNewObject(forEntityName: "Employee", into: self.managedObjectContext)
}
return singularEmployee
}
Then, add this line of code to applicationDidFinishLaunching
singularEmployee()
I work in a team of 25 developers. We use ExtJS MVC pattern of Sencha. But we believe that their definition of MVC is misleading. Maybe we might call their MVC an anti-pattern too.
AMAIK, in MVC controller only knows the name or the path of the view, and has no knowledge on the view's internal structure. For example, it's not the responsibility of the controller, whether view renders the list of customers a simple drop down, or an auto-complete.
However, in Ext JS's MVC, controller should know the rendering of view's elements, because controller hooks into those elements, and listens to their events. This means that if an element of the view change (for example a button become a link), then the relevant selector in the controller should change too. In other words, controller is tightly-coupled to the internal structure of the view.
Is this reason acceptable to denounce Ext JS's MVC as anti-pattern? Are we right that controllers are coupled to views?
UPDATE (March 2015): Ext 5.0 introduced ViewControllers that should address most of the concerns discussed in this thread. Advantages:
Better/enforced scope around component references inside the ViewController
Easier to encapsulate view-specific logic separately from application flow-control logic
ViewController lifecycle managed by the framework along with the view it's associated with
Ext 5 still offers the existing Ext.app.Controller class, to keep things backwards-compatible, and to give more flexibility for how to structure your application.
Original answer:
in Ext JS's MVC, controller should know the rendering of view's elements, because controller hooks into those elements, and listens to their events. This means that if an element of the view change (for example a button become a link), then the relevant selector in the controller should change too. In other words, controller is tightly-coupled to the internal structure of the view.
I actually agree that in most cases this is not the best choice for the exact reasons you cite, and it's unfortunate that most of the examples that ship with Ext and Touch demonstrate refs and control functions that are often defined using selectors that violate view encapsulation. However, this is not a requirement of MVC -- it's just how the examples have been implemented, and it's easy to avoid.
BTW, I think it definitely can make sense to differentiate controller styles between true application controllers (control app flow and shared business logic, should be totally uncoupled from views -- these are what you're referring to), and view controllers (control/event logic specific to a view, tightly-coupled by design). Example of the latter would be logic to coordinate between widgets within a view, totally internally to that view. This is a common use case, and coupling a view-controller to its view is not an issue -- it's simply a code management strategy to keep the view class as dumb as possible.
The problem is that in most documented examples, every controller simply references whatever it wants to, and that's not a great pattern. However, this is NOT a requirement of Ext's MVC implementation -- it is simply a (lazy?) convention used in their examples. It's quite simple (and I would argue advisable) to instead have your view classes define their own custom getters and events for anything that should be exposed to application controllers. The refs config is just a shorthand -- you can always call something like myView.getSomeReference() yourself, and allow the view to dictate what gets returned. Instead of this.control('some > view > widget') just define a custom event on the view and do this.control('myevent') when that widget does something the controller needs to know about. Easy as that.
The drawback is that this approach requires a little more code, and for simple cases (like examples) it can be overkill. But I agree that for real applications, or any shared development, it's a much better approach.
So yes, binding app-level controllers to internal view controls is, in itself, an anti-pattern. But Ext's MVC does not require it, and it's very simple to avoid doing it yourself.
I use ExtJS 4's MVC everyday. Rather than spaghetti code, I have an elegant MVC app that has tightly defined separation of concens and is ridiculously simple to maintain and extend. Maybe your implementation needs to be tweaked a bit to take full advantage of what the MVC approach offers.
Of course the controllers are bound to the views in some way. You need to target exactly which elements in your views you want to listen to.
eg: listen to that button clicks or to that form element change or to that custom component/event.
The goal of MVC is components decoupling and reusability and the Sencha MVC is awesome for that. As #bmoeskau says, you have to be careful in separation of the view controllers (builtin for the view/widgets itself) and the application controllers (top level views manipulations) to take full advantage of the MVC pattern. And this is something not obvious when your read http://docs.sencha.com/ext-js/4-1/#!/guide/application_architecture. Refactor your MVC approach, create different controllers, create custom component, and embrace the full ExtJS MVC architecture to take advantage of it.
There's still a slight problem in Sencha approach IMHO, the MVC refs system doesnt really work when you have multiple instances of the same views in an Application. eg: if you have a TabPanel with multiple instances of the same Component, the refs system is broken as it will always target the first element found in the DOM... There are workarounds and a project trying to fix that but i hope this will be adressed soon.
I'm currently undergoing the Fast Track to ExtJS 4 from Sencha Training. I have a strong background in ExtJS (since ExtJS 2.0) and was very curious to see how the MVC was implemented in ExtJS 4.
Now, previously, the way I would simulate kind of a Controller, would be to delegate that responsibility to the Main Container. Imagine the following example in ExtJS 3:
Ext.ns('Test');
Test.MainPanel = Ext.extend(Ext.Container, {
initComponent : function() {
this.panel1 = new Test.Panel1({
listeners: {
firstButtonPressed: function(){
this.panel2.addSomething();
},
scope: this
}
});
this.panel2 = new Test.Panel2();
this.items = [this.panel1,this.panel2];
Test.MainPanel.superclass.initComponent.call(this);
}
});
Test.Panel1 = Ext.extend(Ext.Panel, {
initComponent : function() {
this.addEvents('firstButtonPressed');
this.tbar = new Ext.Toolbar({
items: [{
text: 'First Button',
handler: function(){
this.fireEvent('firstButtonPressed');
}
}]
});
Text.Panel1.superclass.initComponent.call(this);
}
});
Test.Panel2 = Ext.extend(Ext.Panel, {
initComponent : function() {
this.items = [new Ext.form.Label('test Label')]
Test.Panel2.superclass.initComponent.call(this);
},
addSomething: function(){
alert('add something reached')
}
});
As you can see, my MainPanel is (besides the fact that is holding both panels) also delegating events and thus creating a communication between the two components, so simulating sort of Controller.
In ExtJS 4 there is MVC directly implemented in it. What really striked me was that the way the Controller actually fetches the components is through QuerySelector which in my opinion is very prone to error. Let's see:
Ext.define('MyApp.controller.Earmarks', {
extend:'Ext.app.Controller',
views:['earmark.Chart'],
init:function () {
this.control({
'earmarkchart > toolbar > button':{
click:this.onChartSelect
},
'earmarkchart tool[type=gear]':{
click:this.selectChart
}
});
}
});
So as we can see here, the way the Controller is aware of the earmarkchart button and tool is through selectors. Let's imagine now that I am changing the layout in my earmarkchart and I actually move the button outside of the toolbar. All of a sudden my application is broken, because I always need to be aware that changing the layout might have impact on the Controller associated with it.
One might say that I can then use itemId instead, but again I need to be aware if I delete a component I will need to scatter to find if there is any hidden reference in my Controllers for that itemId, and also the fact that I cannot have the same itemId per parent Component, so if I have an itemId called 'testId' in a Panel1 and the same in a Grid1 then I would still need to select if I want the itemId from Panel1 or from the Grid1.
I understand that the Query is very powerful because it gives you a lot of flexibility, but that flexibility comes at a very high price in my opinion, and if I have a team of 5 people developing User Interfaces and I need to explain this concepts I will put my hands on the fire that they will make tons of mistakes because of the points I referenced before.
What's your overall opinion on this? Would it be easier to just somehow communicate with events? Meaning if my Controller is actually aware of what views he's expecting events, then one could just fire an event dosomethingController and the associated Controller would get it, instead of all this Query problem.
I think if you use the Sencha Architect to produce the Views then Inherit from that View to create Your own View.
Now this View Can be responsible to hook up to any events and raise meaningful events.
This is just a thought...
//Designer Generated
Ext.define('MyApp.view.MainView', {
extend: 'Ext.grid.GridPanel',
alias: 'widget.mainview',
initComponent: function() {
}
});
//Your View Decorator
Ext.define('MyApp.view.MainView', {
extend: 'MyApp.view.MainViewEx',
alias: 'widget.mainviewex',
initComponent: function() {
this.mon(this, 'rowselect', function(){
this.fireEvent('userselected', arguments);
}, this);
}
});
I think there is a pretty bad problem here - its very difficult to shard isolated units within a page.
The approach I'm experimenting with (which makes it somewhat easier to write tests aswell) is to have a vanilla js context object for each page which contains the logic (and has the benefit of being very easy to break up and delegate to different objects). The controllers then basically call methods on the context objects when they receive events and have methods on them for retrieving bits of the view or making changes to the view.
I'm from a wpf background and like to think of the controllers as code-behind files. The dialog between presenter/context and view is a lot chattier than wpf (since you dont have binding + data templating) but its not too bad.
Theres also a further problem I haven't had to solve yet - the use of singletons for controllers causes problems for reuse of UI elements on the same page. That seems like a serious design flaw. The common solution I've seen is (yet again) to pile everything into one file and in this case to ditch the controller altogether. Clearly that's not a good approach as soon as things start to get complicated.
It seems like getting all the state out of the controller should help though and you'd then have a second level of context objects - the top level one would basically just assign a unique id to each view and have a map of context=>view and provide dispatch to the individual context methods - it'd basically be a facade. Then the state for each view would be dealt with in the objects dispatched to. A good example of why statics are evil!
I have built the tree view using third party javascript plugins. I have also use the web templates for my asp.net MVC 3 application. And use Layout view linking to lot of css and javascript.In my category view I want to display the tree view. But the due to script of layout view the tree view is interrupted and not displaying properly. When I put Layout = Null, it shows properly. How can I set priority to the link of script and css link for displaying tree view properly
Take a look at ClientDependancyMvc NuGet package.
It allows to set priority to clientside resources like this:
Html.RequiresCss("Bootstrap/bootstrap.min.css", "Content", 2);
Html.RequiresCss("Bootstrap/bootstrap-responsive.min.css", "Content", 3);
Html.RequiresJs("jquery/1.7.1/jquery.min.js", "googleCDN", 1);
Html.RequiresJs("jqueryui/1.8.18/jquery-ui.min.js", "googleCDN", 2);
Where the last parameter is priority of inserting element into page. More info here.
fairly new to javascript and backbone Marionette, and I cant seem to figure out how to do this.
I want to select a child view from a compositeView by index (or any of the other selectors the docs say are available for the inherited collectionview (from babysitter).).
ie from within myCompositeView:
someMethod: function(index){
this.children.findByIndex(index);
},
...
how can I access the collectionView from a compositeView such that I can findByIndex or findByModel etc and get a reference to the actual Marionette View?
thanks.
Make sure you're using v1.0.0-beta6 of Marionette, as this is where the feature you need was introduced.
CompositeView extends directly from CollectionView, so calling this.children.findByIndex should work, as long as you're using the right version of Marionette.
I have a region named "ActiveModule" and want to re-use it with different views, for example you press the search button and I show the search view in there, etc. etc.
The only way I can ATM do that is to deactivate all the active views in that region and then activate the view I like, this is a bit dirty, is there a "viewManager" or something similar I can use?
If your region is a ContentControl or derives from ContentControl, then there can only be one active view at a time, and you only need to activate the search view on the region.
Did you consider to use a type of contentControl that is able to show multiple views?
For example you can use a TabControl like this:
<TabControl Name="MainRegion" Regions:RegionManager.RegionName="MainRegion"/>
You can now add more than one view to the region. Use INavigationAware and IActiveAware interfaces from Prism to be able to do navigation on the views (activate them, find the correct view etc.).
If you are using a IRegionManager, you can remove all of the views whose types you recognize and then add your own.
foreach (var view in _regionsManager.Regions["MyRegion"].Views.ToArray())
{
if (view is MyType ||
view is MyOtherType)
_regionsManager.Regions["MyRegion"].Remove(view);
}
_regionsManager.AddToRegion("MyRegion", typeof(MyView));
Its by no means ideal, but it works. :)
To my knowledge what you are doing is the only way, theoretically in SCSF the top most view was activated by the framework. You could create ur own ViewManager or a ShowViewService equivalent to get this done. MAtter of fact, thats what i have done!
Not sure how you laid out your framework but if you are using navigation related framework you can simply call
regionManager.RequestNavigate(RegionNames.MainContentRegion, new Uri("your target view" + parameters, UriKind.Relative));
the above line will take care of deactivating other views in the region.
Otherwise if you do view discovery or view injection you can use the approach here
region.Activate(view);