I have a toys controller which users can use to claim toys to play with. Right now, the claim method is implemented in the controller level (as this answer suggested I do).
However, now it's getting a bit fat with claiming logic that really shouldn't be there: A child can't claim a toy if they already have 3 toys, a child can't claim a toy claimed by another child, and so on. The sensible spot for that logic (in my mind) is in the child model, because I'm describing the behavior of a child (what they may and may not do).
That said, if I do this, the toys#claim controller action is going to call methods from the child model. Is this a code smell/bad practice?
(I'm guessing someone's going to suggest I use a service object for this. If you do, could you please point out a simple tutorial? The recent RailsCast about this is a bit too complicated for me.)
Thanks in advance!
In general (outside of Rails), it is not a smell at all. In fact, I'd argue that having a pure 1:1 mapping between "models" and "controllers" is a smell.
Note: I am not a ROR dev. I have no experience in ROR or how it implements things. However, I do understand design patterns quite well, and understand application architecture. With that said:
Instead of worrying about 1:1 mappings, step back and think about the structure of the application.
What is the Controller supposed to be doing? Well, in general it is supposed to route user actions to the application. It is just a plumbing step.
Then what is a Model (layer) supposed to be doing? In general, the Model is a layer that encompasses all of your business logic in the application. It will handle database interaction, access controls, business operations, etc. Therefore, the model is actually the vast majority of your application.
The View on the other hand is your presentational layer. It should handle all rendering, pulling data from the model layer.
Based on that understanding, your models, views and controllers should be able to vary independently to each other. In general, I'd expect to see a fairly 1:1 relationship between controllers and views. What I mean by that is that each controller that exists, I'd expect to see a view. But there can be views that exist where there's no user interaction. In those cases, you may need a controller (to render the view), or depending on your architecture, you many not need one.
But the "model classes", which are a small part of the model layer (acting as proxies or adapters for the lower model functionality) may or may not be 1:1 with controllers or views. For example, you may have a view that pulls data from multiple models. You can have a controller which acts on multiple models.
Now you could step back and say that if a controller needs to act upon multiple models, then create a new model which abstracts that operation. Sometimes that is the right thing to do. Sometimes it's not. It all boils down to the specific operations and relationships involved...
At the end of the day, there's no "right" or "wrong" here. It really comes to a design decision that you need to make as you structure your application. I wouldn't worry too much about the "smell" component, as long as it makes sense in your application...
At my new job, I was given some MVC work. There is only one controller with nine action methods(6 are for ajax rendering) . The page was bit large, so I divided it into small your controls and used render partial to render them. Some user controls were being render through ajax also. Most of the controls are not more like foreach loops and rendering some data from tables, not more 10-15 lines. The main index page passes model to all the controls. My main page looked very clean and easy to maintain.
But my team members are saying, I should put everything in the main page rather than building small controls. Their point is number of files will be a lot, if we start creating controls like this. Also they say if we are not reusing these controls somewhere else there is no point creating them separately.
I would like to know what is better approach for this kind of scenario. Any good links which can help us to understand things better, or any book we can read to clarify our questions.
Help will be appreciated.
Regards
Parminder
As a preface to my answer, let me mention the important value of maintainability. Software evolves over time... and must change to fit the need of the application.
Maintainability in code does not magically appear... Sacrifices (with a touch of paranoia sometimes) must be made in your coding style now, to have the flexibility you'd like in the future.
There may a large page in your project. Some may say that if it works, no need to fix it. But that's looking at it from a short term perspective. You may need some of those UI interfaces in other places in the future. What some persons may do (rather than make partials) is copy that code in the places where they need it - thus causing the same bloat over time that they were trying to avoid.
If you're on the project in the long haul, you'll more fully appreciate the need for flexibility over time. You can see that there are patterns that you'll want to re-use.
My suggestion then: Partials and controls are good things... they are good investments for your ease in the future. If you forecast reusability, that's a good sign for using them.
But use them sparingly. Don't micromanage everything on a page. Some things may be itching to be 'component-ized' but sometimes it's best to SSFL (Save some for later). Like everything in life, balance is important.
Having clean concise code is the way to go. Your code will be alot more readable if you utilize :
sections
templates
partial views
Just remember its always easier to navigate folder structure than to read 100's - 1000's of lines of code.
I recommend watching "Putting your controllers on a diet" by Jimmy Bogard.
Also read "Fat Controllers" by Ian Cooper.
these two links will give you a good idea on how to structure your MVC apps.
I come from an MVC background (Flex and Rails) and love the ideas of code separation, reusability, encapsulation, etc. It makes it easy to build things quickly and reuse components in other projects. However, it has been very difficult to stick with the MVC principles when trying to build complex, state-driven, asynchronous, animated applications.
I am trying to create animated transitions between many nested views in an application, and it got me thinking about whether or not I was misleading myself... Can you apply principles from MVC to principles from Artificial Intelligence (Behavior-Trees, Hierarchical State Machines, Nested States), like Games? Do those two disciplines play nicely together?
It's very easy to keep the views/graphics ignorant of anything outside of themselves when things are static, like with an HTML CMS system or whatever. But when you start adding complex state-driven transitions, it seems like everything needs to know about everything else, and the MVC almost gets in the way. What do you think?
Update:
An example. Well right now I am working on a website in Flex. I have come to the conclusion that in order to properly animate every nested element in the application, I have to think of them as AI Agents. Each "View", then, has it's own Behavior Tree. That is, it performs an action (shows and hides itself) based on the context (what the selected data is, etc.). In order to do that, I need a ViewController type thing, I'm calling it a Presenter. So I have a View (the graphics laid out in MXML), a Presenter (defining the animations and actions the View can take based on the state and nested states of the application), and a Presentation Model to present the data to the View (through the presenter). I also have Models for value objects and Controllers for handling URLs and database calls etc... all the normal static/html-like MVC stuff.
For a while there I was trying to figure out how to structure these "agents" such that they could respond to their surrounding context (what's selected, etc.). It seemed like everything needed to be aware of everything else. And then I read about a Path/Navigation Table/List for games and immediately thought they have a centrally-stored table of all precalculated actions every agent can take. So that got me wondering how they actually structure their code.
All of the 3D video game stuff is a big secret, and a lot of it from what I see is done with a graphical UI/editor, like defining behavior trees. So I'm wondering if they use some sort of MVC to structure how their agents respond to the environment, and how they keep their code modular and encapsulated.
"Can you apply principles from MVC to
principles from Artificial
Intelligence (Behavior-Trees,
Hierarchical State Machines, Nested
States), like Games?"
Of course. 99.9% of the AI is purely in the Model. The Controller sends the inputs to it, the View is how you represent it on the screen to the user.
Now, if you want to start having the AI control something, you may end up nesting the concepts, and your game 'model' contains a Model for an entity, a Controller for the entity which is the AI sending commands to it, and a View for the entity which represents the perceptions of that entity that the Controller can work with. But that's a separate issue from whether it can 'play nicely'. MVC is about separating presentation and input from logic and state and that aspect doesn't care what the logic and state looks like.
Keep this in mind:
The things which need to react simply have to be aware of the things to which they need to react.
So if they need to know about everything, then they need to know about everything.
Otherwise, -how- do you make them aware? In 3D video games stuff, say first-person shooters, the enemies react to sound and sight (footsteps / gunshots and you / dead bodies, for instance). Note that I indicated an abstract basis, and parts of the decision tree.
It might be wrong in your specific case to separate the whole thing between several agents, and simpler to leave it to one main agent who can delegate orders to separate processes (/begin babble) : each view could be a process which could be told to switch to any (a number of) view by the main agent, depending on what data the main agent has received.
Hope that helps.. Take it all with a grain of salt :)
It sounds like you need to make more use of the Observer/Event Aggregator pattern. If multiple components need to react to arbitrary application events without introducing undue coupling, then using an event aggregator would help you out. Example: when an item is selected, an application event is published, relevant controllers tell their view to run animations, etc. Different components aren't aware of others, they just listen for common events.
Also, the code that makes the view do things (launch animation depending on model/controller state) - that's part of the View itself, so you don't have to make your architecture weird by having a controller and a viewcontroller. If it's UI specific code, then it's part of the view. I'm not familiar with Flex, but in WPF/Silverlight, stuff like that would go into the code-behind (though for the most part Visual State Manager is more than enough to deal with state animations so you can keep everything in XAML).
At my company we're about to build a new site using ASP.NET MVC. My boss (marketing guy) would like to know some more about the technology so I've tried to find a really good, simple and pedagogical presentation of the MVC concept without any luck. Most of them require quite a lot of basic knowledge in programming.
Any suggestions for a good video, slides or other?
Craig Strong has a pretty nice article about MVC in general and how to explain its benefits to business. Check it out here: Updated link.
Define MVC in layman’s terms
Remember you’re technically minded and close to the code. MVC to you
is as clear as day, but saying to the business ‘Model, View,
Contoller’ could give them the impression that you are suffering from
some form tourette syndrome. MVC won’t mean much to the business even
after you define them in relation to the code. To get the business to
understand why this is the answer and least of all what it is, can be
more of a task than expected in my experience. Even some fellow
developers have difficulty understanding this on occasion.
To get the listener to understand what MVC is and why it works what I
have tried in the pass is to apply MVC to a different industries where
the listeners have had more involvement. An example that has worked
for me in the past in a comparison to the property or even the
vehicles. Most people have had dealing’s with builders, carpenters,
plumbers, electricians or have watched the flood of property shows on
the TV. This experience is a good platform to use and to explain why
separation such as MVC works. I know you’re probably thinking that
won’t work as it’s not the same as in software, but remember you’re
not trying to train the business to become developers or have an in
depth understanding of MVC, simply explaining to them that separation
in production is required and that’s what an MVC structure offers.
To give an example of how you could describe this I have very briefly
explained how separation works in property. Keep in mind this is
focused on using the system not developing which could be a completely
different angle of explanation.
View
The view in MVC is the presentation layer. This is what the end user
of a product will see and interact with. A system can have multiple
views of all different types ranging from command line output to
rendered HTML. The view doesn’t consist of business logic in most
clear designs. The interface is fit for purpose and is the area of
interaction. Therefore you could simply output HTML for consumers to
interact with or output SOAP/XML for businesses to interact with. Both
use the same business logic behind the system otherwise known as the
models and controllers.
In the world of property you could think of the view as the interior
of a property or the outer layer of a property that the inhabitants
interact with. The interior can be customised for purpose and the same
property can have many different types of tenants. For example a
property of a particular design could contain residential dwellings.
The same internal space could easily be used as office space, where
although in the same property has a different purpose. However the
property structure is the same. Therefore the environment in which the
users interact does not interfere with the structure of the building.
Controllers
The controller is where the magic happens and defines the business
application logic. This could be where the user has sent a response
from the view, then this response is used to process the internal
workings of the request and processes the response back to the user.
Taking a typical response where a user has requested to buy a book.
The controller has the user id, payment details, shipping address and
item choice. These elements are then processed through the business
logic to complete a purchase. The data is passed through the system
into the model layer and eventually after the entire request satisfies
the business definitions, the order is constructed and the user
receives their item.
If we compare this to a property, we could compare the ordering of a
book online to turning on a light switch. A tenant will flick the
switch to on just like ordering a book. The switch itself is an
element in the view layer which sends the request to the controller
just like clicking a checkout button on a web site. The business logic
in this case is what the electrician installed and are embedded within
the property designs. The switch is flicked, which completes the
circuit. Electricity runs through all the wires including the fuse box
straight through to the light bulb. Just like the user receiving a
book, in this case the tenant receives light. The whole process behind
the scenes involving the electricity cabling is not visible to the the
tenant. They simply interact with the switch within the space and from
there the controller handles the request.
Models
The models in MVC are the bottom most layer and handle the core logic
of the system. In most cases this could be seen as the layer that
interacts with the data source. In systems using MVC, the controller
will pass information to the model in order to store and retrieve
data. Following on from the example above controller definition, this
is where the order details are stored. Additional data such as stock
levels, physical location of product of the book amongst many things
are all stored here. If that was the last book in stock ordered, the
next request for this item may check if it’s available and disallow
the order as the item is no longer available.
Sticking with our example of turning on a light switch, this level in
our structure could be the electricity supply. When the tenant flicks
the switch, the internal circuit must request electricity to power the
request which is similar when the user requested data from the
database, as in data is needed to process a request. If the dwelling
isn’t connected to an electric supply, it cannot complete the process.
Business benefits from using MVC
After you get the message across explaining what MVC is, you will then
have to see what benefits can be obtained from it. I’m not going to go
into a huge amount of detail here are I’m sure you can apply benefits
more accurately which are directly related to you actual situation. To
list just some of the common benefits of an MVC based system here are
a few examples:
Different skill levels can work on different system levels. For example designers can work on the interface (View) with very little
development knowledge and developers can work on the business logic
(Controller) with very little concern for the design level. Then they
simply integrate together on completion.
As a result of the above separation projects can be managed easier and quicker. The designer can start the interfaces before the
developer and vice versa. This development process can be parallel as
opposed to being sequential therefore reducing development time.
Easy to have multiple view types using the same business logic.
Clear route through the system. You clearly know where there different levels of the system are. With a clear route of the system,
logic can be shared and improved. This has added security benefits as
you clearly know the permitted route from the data to the user and can
have clear security checks along the route.
Each layer is responsible for itself. (Relates to point 1) This means that you can have clean file structure which can be maintained
and managed much easier and quicker than a tightly couple system where
you may have lots of duplicate logic.
Having a clear structure means development will be more transparent which should result in reduced development time,
maintenance problems and release cycles if applied properly.
M-V-C Think of it as:
"Order Details (including Customer & Employee info)", "HTML/ASP Form (to display the OrderDetails)" and "Order details service class (having methods to SaveOrderDetails, GetOrderDetails etc.).
The Model (Data Class e.g. OrderDetails)
The data you want to Display
The Controller (Service class)
Knows about the Model (Order Details)
Has methods to manage the Model
And as such can be unit tested Its Single Responsibility is to manage the OrderDetails CRUD operations.
It knows NOTHING about the View
The View (ASP Page)
Displays the Model (OrderDetail's ViewData).
It has to know about the Model's structure so it can correctly display the data to the users on screen.
The View's structure (style, layout, HTML etc., locale) can be changed at anytime without it changing anything in the application's functionality.
And as such, many Views can display the same Model in many different ways.
In multi-tenant web applications, Customer specific Views can be stored in a database table and displayed based on Customer information
You have to explain the benefits of ASP.NET MVC, not the features
You have control over your URLs -- that means SEO for the site will be better -- that means your site will be higher in google
The code is cleaner, which means that it's easier to change, which means that you can add features faster
etc.
How do you save money, make money, reduce risk? That's what your boss wants to know.
Imagine a control room in a factory, the model is the machine itself, the monitoring equipment is the view and the instrument panel is the controller. You could have several different control rooms for the same machine and changes in the controls in one control room would reflect on the monitors in all control rooms.
The point is that you should only model once and then view or control however is most convenient.
The model is the data access layer, which can just be a wrapper for a few simple queries to an ORM that manages the data entity relationships itself. It handles communication to the data source, retrieves data and usually organizes it into objects defined in your application.
The views are just html files with bits of html and css with some templating engine (smarty, mako, etc) code to display the data passed to it the way you want.
The controller puts it all together. Requests made to your page will be routed to a controller (class) and an action (method) within the controller. Just like any other application, the action will do what's requested of it, but it's still part of the controller.
So, the controller uses the model to query data (users, content, etc), then passes the data to a view to be rendered and displayed the way you want.
I wouldn't try to explain the technology to him, I'd try to explain what the MVC architectural principle is all about.
MVC was designed to separate concerns. Plain and simple. Explain to him that when you build anything that what you're building can be classified in two different categories: what the business need is (the domain), and everything else.
MVC separates the Domain from the everything else by introducing layers to separate out the concerns. M is for Model, which is your domain. V is for View, which is the visible part to him, what he sees. C is for Controller, the part that controls what is going on in between the Domain and the View.
The marketing guy would just be interested in the "V" part, the View. Depending on how you design things, the View would just be basic HTML/CSS "templates" that the marketing person could modify. Technically without breaking anything.
Ideally the Model (database) and Controller (logic) shouldn't care if the View (presentation) is XML, HTML, text, etc. The marketing person shouldn't care what the Model and Controller do, except for requesting additional functionality.
Going further with the "ideal", you should technically be able to replace ASP with PHP, Java, Ruby, etc as the Controller without touching the Model or View.
You can very easily do this, that is if you understand marking speak. I dont but I imagine it would go something like this...
This should be use. MVC (if done right) will allow you to decouple the UI from the data (model) and control of the UI (controler). This will allow the UI to be more flexible which will in turn allow to better market it self faster.
To a marketing guy, perhaps the best way to explain the reason for ASP.Net MVC is the ability to broaden your product's reach.
By using MVC, the code is already separated in a fashion that will let you more easily build an interface that feels natural on a desktop, and then the different interface that caters to a general mobile device user, and a still-slightly-different interface that caters to an iPhone user, without risking the backend code getting out of sync and introducing subtle and company-harming bugs. And, if there's a smart client desktop app that could be a product... it, too, can rest on the same codebase.
The Model is "how things work inside the box". The Controller is "what you can touch on the outside of the box" and the view is "what comes out of the box"...
The most important thing for your marketing guy is money, budget, TCO ...
When you don't use MVC you usually mix design, application logic etc. alltogether.
Programmer then must know html design, programming etc... That could mean you need powerful professional to do it all.
if you use MVC, everything is divided into "separate parts". Html coder can prepare html layer, programmer only works with application logic etc...
MVC brings better granularity and everybody can focus on what he or she can do the best!
Listen, for example xhtml validity and css cleanliness is so hard that there is a lot of people who focuses only on this while lot of browsers and platforms compatibility on mind.
Usually one person is NOT the best asp.net programmer, xhtml coder in one ;-)
This is a pretty simple one
http://en.wikipedia.org/wiki/Model-view-controller#Pattern_description
The best way I can thing of is that the model is the data representation, the view is the presentation to the user and the controller is what collects user interaction that changes the model.
The important word in the title of the manager in this case is "marketing." He is a Marketing manager. The concerns one has as a marketing manager have to do with strategy and tactics. These two are not the same thing. Strategy is the big picture word that embraces among other things how a company conceptually addresses customer needs and how the company differentiates itself from its competition. Strategy is typically not what software can portray to a user. Tactics, on the other hand, are the direct methods or approaches that a company takes in winning the business of the customer. Tactics tend to change far more frequently than strategies, and it is likely that the marketing manager, when he asks what advantage MVC may give him, is really asking, "How rapidly can you change whatever it is that you create into something that conforms to new realities in the way we have to deal with customers." In other words, how quickly can you change an offer of "buy 1 and get 1 free" into "buy 2 on Friday and get 1 on the following Tuesday if it is raining in Albany."
Marketing management is about results measured in dollars and cents, not finery and nuanced explanations that are littered with conceptual words lacking any real specificity. Everything a programmer may say might make sense to himself, but a marketing manager needs to know the real likelihood of rapid response to changing customer perceptions or rapid implementation to a different approach to selling to the same customers. He needs to know if it will cost more than an existing method because if he sells $1 million more in product while spending $1.25 million in software development, he will probably lose his job.
So, in short, he is looking for flexibility and cost-effectiveness. He needs software that be adapted to changing conditions quickly, just as he changes his pitch first one way and then another to a difficult-to-persuade prospective customer, and he needs to know that he won't have to be liable for a huge price tag for that flexibility.
Frankly, I don't think that you would be able to deliver on such promises if they were made because in spite of all the advantages of MVC from a development point of view, we are still talking about software here, and as we all know, software is a rigid, demanding taskmaster that takes it own sweet time to mature to the point of trustworthiness and to be rid of its bugs. We as programmers are always in search of the holy grail of software reusability, and while we flail about trying one thing and then another (MVC, MVP, MVVM, and whatever else someone may conceive), the rest of the world is simply asking for something that works. So the best of luck to you. I hope you are able to win your case.
I want to support just 2 languages. There will be no requirement for any additional language. What will be the best approach after considering both ease of use and maintenability:
(a) Each view has a separate page for each language and they will share controllers and model dlls
(b) Both languages pump resources into the same view template
Please don't bother about the url structure right now. I will appreciate real experiences over the theoretical discourses of pros and cons. Thanks for your help.
Mutliple views are more flexiable clearly and if you only have 2 then that is a possibility but its still a pain.
However having just 2 instead of N to worry about means you can probably take both into consideration when creating the views in the first place. Hence instead creating multiple views create a single view that uses resources and works in both languages.
Depends on how different you expect the localized versions to get. If you are pretty confident they will always be almost identical, simply different words in each placeholder, then a single view model would probably be the way to go.
However, what I have found to work when there is a blend between the two (i.e. some views are the same, just translated; others end up being somewhat different) is to build a provider model into each view and sub-view, so when the view engine goes to load a view, there is isolated logic in the provider factory to determine, for that particular view, whether to use the same for both languages or switch.