When using the MVC pattern, should I implement a seperate controller for each view?
Create a new one if you need to. Don't if you don't.
Patterns are not about data structures, they're about organizational patterns among communicating components. If the same controller is appropriate for more than one view, great - especially if you can use it without modification.
If you have to change it, then you have a case for two separate controllers. If there is shared code between them, then consider moving it to another class - either a base class or (my personal preference) shared via aggregation.
The easiest way to think about MVC is a command-line program. The program is the Model. The Controller is STDIN. The View is STDOUT.
I believe there is no 'the' MVC pattern. There are almost as many MVC patterns as there are users of a MVC architecture. That being said, in my opinion, the answer to your question is 'no'.
I use to implement a controller for each module of my application, not for each view. A controller can call methods of other controller. I'm not sure if this is the better way to do it, but I think It's working well for me.
the idea is to separate/decoupling M, V and C, its not a problem if you want a single controller control multiple view, as long as the view and controller is decoupled
Related
While working with Unity, I realized that separating Model and View would make my code more readable and straightforward. Constructing the whole model, all I had to do is just create some UI and bind it to Model.
But I still don't understand what 'Controller' is, and why does it exist. I don't think I had trouble when I directly bound View to Model, not through Controller.
So the question is if we can bind View to Model directly, why do we need Controller? What's the benefit of having Controller between Model and View?
At the highest level the Controller is the link between the View (displaying the UI/UX) and the Model (creating and managing your database and its tables).
True, it is possible to write code without any Controller usage but your Views will quickly get very cluttered and each file will be full of logic that is much more nicely stored somewhere else hint hint.
The Controller (and Model and some other places such as helpers) is thus the perfect place to sort out all the back-end code so that all you need to do is send a single field or object to your View to display.
An example is somewhat painful because by its nature the Controller is where you go to sort out your code as things get more complicated but this is a great article to get you on the right track! HTH
https://www.toptal.com/unity-unity3d/unity-with-mvc-how-to-level-up-your-game-development
I don't have years of experience, but in my understanding controllers provide a bridge across view and models. While view contain the pretty part and models contain useful parts the controller do the calls of functions passing values from database to view or inputs to model. That provide a way to avoid lots of injection like class A calling class B, calling class C, etc.
You can put rule business in controllers or in view, but thats not the expected in MVC architecture. The first important thing (for me) in software programming is readability, whats MVC provide.
if you've interest, search for other architectures like MVVM, to compare then.
Please enlighten me: If I'm implementing a simple application using MVC pattern, should controllers always be bound to objects existing in the application?
For example, if I'm implementing a Holiday Reservation Application and I specify such classes like: User, HolidayRequest, Holiday, etc, should the controllers be: UserController, HolidayRequestController and HolidayController?
Thank you for your help.
Your controller receives the input of your application and controls what happens with this input (i.e. which data is passed to the model, which actions the model should execute on it, and perhaps if the view needs to update itself).
The inputs I can see in your example are a HolidayRequest, and a HolidayReservation. Those would be separate actions on your controller, so I would create a HolidayController that implements those actions.
In general, I would recommend going for a keep it simple approach, if your application is not too complex, your architecture should be simple, too. Don't go implementing N controllers when all you need is one single class ;-)
I would highly appreciate it if someone can share their thoughts on this. I am new to Spring, but not new to MVC. However, my exposure with MVC has mostly been on the front-end side of things.
Lets say if I have a dynamic site which employs SpringMVC Framework 3.0, and site has 5 links such as:
HOME | FAMILY | COMEDY | HORROR | ACTION
Each of these links would query a database and display information. If I was to be doing this for front-end via a MVC framework, I would have five different controllers, but I came across a question here (Stackoverflow) which talks about having just one controller and then numerous resolvers. I would like to know what is the correct approach?
Here is the link to the mentioned question:
Spring controller setup question?
As Jaanas said, it really depends on how you are retrieving the data for each link and whether the resulting pages are all based on the same data model and templete (JSP) or are completely different to each other.
I tend to use a separate controller for "home" but if those other pages are simply querying a database then, I'd start serving those from a single controller.
Its also a good idea to try and think of your pages in terms of REST principles. Once you start seeing the links in terms of REST URIs, then the decision of whether the various URIs go in the same or separate controllers is obvious. E.g. if the URI for "family" is /movie/genre/family, then it becomes clear that all 4 of those links should go in the GenreController class (or a MovieController class, with a /genre method capturing the category with a #PathVariable annotation).
It depends on how much logic you have behind each link. If you have only one mapping in each controller, you could use single controller.
That said, I still prefer having separate controllers, when doing only small project like yours.
On the other hand, if your project expands, you could end up having absurd amount of controller, that don't do much. In that case you could group your controllers from start, so grouping similar controllers, that have almost equal logical side.
The number of controllers in your application depends on the scope of your project. If you have fixed requirement and the number of operations are limited then you can use single controller which will handle your all request.
But if your requirements are not fixed or going to increment with your application version, you must use separate controller for separate module. So that in future you can easily manage your application code.
For better code maintenance, I will prefer to use separate controller for each module.
I was originally going to make this a longer question, but I feel like the shorter I make it, the better you'll understand what I mean.
The MVC architectural pattern has 3 dependencies. The View depends on the model. The Controller depends on the View and Model. The Model is independent.
The Layers architectural pattern defines N - 1 dependencies, where N is the number of Layers.
Given three Layers: Model, View, and Controller, there are only 2 dependencies, as opposed to 3 with traditional MVC. The structure looks like this:
View ---> Controller ---> Model
[View depends on Controller, Controller depends on Model]
It seems to me that this style accomplishes the same goals and produces looser coupling. Why isn't this style more common? Does it truly accomplish the same goals?
Edit: Not ASP.NET MVC, just the pattern.
With regard to griegs's post:
As far as mocking, Layers still allows you to use the Command Processor pattern to simulate button clicks, as well as any other range of events.
UI changes are still very easy, perhaps even easier. In MVC, the Controller and View tend to mesh together. Layers creates a strict separation. Both Layers are black boxes, free to vary independently in implementation.
The Controller has 0 dependencies on the View. The View can be written, and time can still be saved with loose coupling.
Because you decouple the interface from the controller making changes easier.
Also consider the scenario where you need to get started on a project but the artwork won't be ready for weeks or months. Do you wait or do you write all the code required for the pages and simply then wire up the view to the controller.
At least that's what we did and we saved months.
Also it made UI changes easier to cope with because there wasn't any code in our aspx pages that did anything.
Our tests were also better as we could mock up anything including button clicks etc.
And if you're talking about the asp.net-mvc framework, there is no code in the aspx files and no viewstate etc.
In proper MVC the controller doesn't depend on the view afaik. Or maybe I'm not understanding it correctly.
The model defines the data.
The view defines what the output looks like.
And the controller is a translator from a model-understood grammar to view-understood grammar.
So essentially the controller is independent. The view is independent. And the model is independent.
Yes? No?
I'll be bold, and try to explain why your method didn't catch on.
The MVC pattern basically requires the view and model layers to agree on an API.
Since one serves the other and there are no dependencies inside the code it leaves the controller to behave generically, all it needs to do is take a certain structure in the view layer and call the matching API on the model layer.
You'll note that agreeing on an API between the view and model isn't really such a big deal it has to happen anyway. And what you get is good separation between back-end front-end development.
In your proposed solution a lot of development is required on the controller side. The controller will be required to understand all the elements in the view and to map them to the specific calls required on the model layer.
Since the controller is a single access point connecting many views to many models this can quickly get out of hand and end up being an incomprehensible controller module.
Look at some Struts2 examples to see what I mean...
I think I'm understanding your point:
Yes you can make the View only depend on the Controller only by making the Controller transform (using PHP as an example) the Model objects to non-Model objects like simple arrays.
As we already know, performing this transformation can be more effort than it's worth if the decoupling isn't actually needed. If the View uses the Model objects then it has this dependency. However, this can be relieved a bit by having the View depend solely on the Controller for its required input, which can be Model objects.
The Symfony PHP framework promotes this style of skinny controller shuffling between Model and View. You can still directly call upon the Model layer to retrieve objects within the View layer but it's strongly urged against for the coupling issues you bring up. Within the View you can call include_component() which actually goes back up to the Controller if you need to query the Model.
I haven't gotten back to this in a long time, mostly because I was still thinking. I was unsatisfied with the answers I received, they didn't really answer my question.
A professor, recently, did steer me in the right direction. Essentially, he told me this: Layers which separate Model, View, and Controller is MVC. In the vanilla MVC architectural pattern, the dependency between the View to the Model is often not used, and you effectively end up with Layers. The idea is the same, the naming is just poor.
Choosing a presentation pattern for a new or enterprise web development on the Microsoft platform is a daunting task, in my opinion there are only three; View Model, Model-View-Presenter (MVP) or ASP.NET MVC (a Model2 derivative).
You can read the full article here ASP.NET MVC Patterns
I'd like to add some more things. First of all for my point of view is we use the model as container for the information we want to pass and show on the view. Usually the action method into the controller ends with return view("viewName",model).The view itself probabily will change its layour against the model :
on the view :
if(model.something==true) {
%>
somethign to show
<%
}
At this poinf the definition of model is hard to find.
I can say (especially on enterprise conext) the are two "model"
one is the domain model/entity model or how you want to call it that wraps the data coming from the lower layers (database,etc) and the view-model who contain the information we wants to show plus any other information we need to hide/show portion of interface
The controller orchestrate the the views and is indipendent from the view but a bit dipendent from the model:
into the controller
pulic actionResult Index(){
....
if(model.BoolProperty==true){
return ("firstView);
}
else
{
return ("secondView");
}
}
I hope it makes sense
In my opinion ,you'd better try it in your programme , you can use ruby on rails ,or codeigniter( for php ),these great framework may be helpful to your understanding the MVC.
If I need two modes in my application what design pattern would I use so I can prevent ugly conditional code? App is currently MVC, but I don't want conditional code in my controllers and don't want two controllers for each view unless I have to.
Any suggestions?
A different subclass for each implementation, with shared functionality either in a common superclass or using the Template Method pattern.
Perhaps the State Pattern?
Abstract Factory, or Proxy. Your controller would contain some kind of Factory or Proxy instance that is used to retrieve a "mode" and act on it accordingly.
It is difficult to say for sure without more information, but I would suggest the strategy pattern. You could use the same controller and just swap out the strategy object to produce the desired change in behavior.
Here is an article you may find useful:
http://www.javaworld.com/javaworld/jw-04-2002/jw-0426-designpatterns.html
take a look at JSR-168, java portlet and its reference implementation, it should be similar to what you are trying to achieve.
The appropriate place for such a decision is the controller of MVC. I would recommend you write it there first. If it really is repetitive, it may be straightforward to figure out how to clean it up: you can move the conditional logic into a base class, or depending on the language, may be able to handle it with some sort of filter. You may also be able to create some "factory" for the views, which understands the "mode" of your application. Architecturally, though, all this is in the controller.
You are right to not want it in the view. This would be pretty messy. You probably want two versions of the views, one for "view" and one for "edit".
In the end, this is what controllers are for. Good luck!
In CafeTownsend demo made with PureMVC there is a similar situation where there are two different views and two separate Mediators. You absolute don't need conditional code for that. I don't know what technology and programming language you are using, but in Flex it will be a ViewStack with the ListView and EditView as children:
Corresponding mediator is registered by demand when the view is created. You can check other implementations using previous link.