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I need to explain to a not-very-technical manager the MVC (model-view-controller) concept and ran into trouble. The problem is that the explanation needs to be on a "your grandma will get it" level - e.g. even the fairly straightforward explanation offered on MVC Wiki page didn't work, at least with my commentary.
Does anyone have a reference to a good MVC explanation in simple terms?
It would ideally be done with non-techie metaphor examples (e.g. similar to "Decorator pattern is like glasses") - one reason I failed was that all MVC examples I could come up with were development related.
I once saw a list of pattern explanations but to the best of my memory MVC was not on it.
Thanks!
How about this - off the top of my head, hopefully it works for you.
MVC can be metaphorically related to a TV. You have various channels, with different information on them supplied by your cable provider (the model). The TV screen displays these channels to you (the view). You pressing the buttons on the remote controls affects what you see and how you see it (the controller).
I was watching TV, so I got some inspiration from there!
I don't trust metaphors. But it's not hard to explain it:
the Model is the part of the code that knows things
the View is the part of the code that shows the things the Model knows
the Controller is the part of the code that gets commands from the user and tells the View what to show and the Model what to know.
The best way I describe it would be:
The Model is the data source. It's your database storage, it's the
code needed to add/remove/update/change the information you
warehouse.
The View is the part the user sees and interacts with. An HTML
page, an application window.
The Controller is the code that marries the View to the Model. If
you clicked a "Delete" button, it handles the business logic and
rules (are you the authorized person to delete? is it a deletable
record, etc).
The View doesn't need to know anything about the Model. The Model doesn't need to know anything about the View. The Controller is what marries the information source (Model) with the output (View).
Think of it in terms of video games. Way back when - there were tons of different video cards and how they worked. Games needed all kinds of code to talk to them. You had to choose what kind of card you had before you could play the game. Game developers had to create code for different video cards.
Along comes something like OpenGL or DirectX -- and it acted as the middle-layer between them. Game developers could write to the DirectX interface -- instead of different card's instruction sets. It freed game developers from having to know about the specific video card. It freed card makers to be able to design to the DirectX instruction set.
In this case - you playing the game is the View, DirectX is the Controller, and the Model is the video card.
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
Tell "your grandma" that you are the model (you are doing the work), he is the controller (i.e., middle manager), and the view is like marketing, they get all the credit.
Related
I have written python code that analyses two text sources and compares them.
I'd like to implement this dynamically via two text boxes that a user could either type into or manually upload. I have already begun coding this using HTML. Would it be better to implement a widget or the models instead to make the text area boxes?
Edit:
I wrote this question when I was just figuring Django out, so forgive me if it sounds confusing. But everyone starts somewhere. I'm unable to delete the question as contributions have been made already. YouTube courses proved helpful in learning the basics, if any beginners stumble upon this.
You use a form object. Django has form objects (https://docs.djangoproject.com/en/2.0/topics/forms) that take a model and translate it into html elements. So I guess in a way, you implement the model but I want to stress that that's not actually what's happening from a technical standpoint. A better way to say it is that you're implementing forms. The reason I stress this so much is so that you understand what's really going on so that you don't have misunderstandings that end up costing you in code clarity and readability.
So to answer your question, you can implement django forms to do this very easily. The way you implement it depends on your models and how they are designed since the forms use the models to create the right html form elements. If you're dealing with one model that will be instantiated by the form input, create a model form. This will take the input from the form and create your model instance. If you're dealing with one form that uses multiple models, then use a generic form. In this case, you will have to write your own save method that does the actual logic of the form.
One other thing to add... No matter what, your end result will always be a widget on the HTML in the end. Django forms translate a model class into a form element with input elements. If you didn't use Django forms, you would still do the translating, but you would have to do it from scratch.
I hope this helps and that I correctly understood your question.
we have a small questionaire application,
and 1 of the main sections is the questionaire itself.
it has a big view for some general templating, introduction and title etc
and it has subviews per question (with next and previous buttons)
we decided to use routing, because from several places one can jump to a specific question
so we use /ivr/4 to show question 4, and /ivr/overview showing the final overview.
so in a way you go from /ivr/1 to /ivr/2 ... to /ivr/overview
now, if one comes from /ivr/1 and arrives on /ivr/2
the big view is there, and it should only update the question to the right question
but when you arrive from /home to /ivr/2
the big view is not loaded, so one should first open the questionaire and then load question 2
currently i have it always rerendering the big view
which works, but is lots of overhead and i would like to refactor this to a better way.
can anyone give me some guidance as to how i would structure routeActions and or views
to only update the big parentview when it actually needs to, and do the question view only, if the parent view is already there.
do i need events?
or would i go with partial routes?
any tip is welcome.
I think both of your proposed solutions sound workable. If you go with events, I'd recommend using the event aggregator pattern to facilitate communication between your views. This seems like the simpler option to me.
The other solution, partial routes, might be more involved. Check out the Backbone.Marionette plugin, which was designed to help manage complex view manipulation.
The title might not be easy to understand but it seems to me it is a basic design question when dealing with smart models.
I have a hierarchy of model objects that represent different types of document.
Say I have a view with different buttons, each one opens the document of the underlying object model. When I click on a button I have to display a view whose controller implementation depends only on the underlying model object class. How do I get this implementation ?
(It could be in the implementation of the button but then the question becomes how do I get the implementation of the button)
Should it be a factory that takes as an input the type of my model and returns my view controller ? Should it be my model that knows how to build its controller (seems dirty nè ?) ? Should I use composition ? Something else ?
I hope I am being clear enough. I am a bit struggling with this !
Your question is too abstract to give a specific advice. MVC pattern appears in many forms and in many technologies. For a web page it will have one shape, for a WPF app it will have another. In general there are both "view-first" and "controller-first" approaches. You can start with any one and see if it comes natural for your problem, if not -- refactor.
One other area you can explore is the area of modern composite application frameworks which provide out-of-the-box modular MVC\MVVM solutions. If you're writing for web, read about ASP.NET MVC and its best practices. If you're writing for WPF, read about MVVM approach and take a look at Prism, for example. You might find that your problem is already solved by existing tools.
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Question: Are there any Mvc framework solutions that I can leverage to create a clean and concise approach that represents my user control that I am converting? (There are four major design considerations listed below)
This user control has a lot of explanatory text information within. I really want to avoid writing a helper method that is a mile long containing a ton of standard HTML and text.
This user control contains a Grid. I have written my on Grid control in Mvc but I have not had any experience as of yet with composition of html helpers in a clean fashion.
This control is only presented to the user as a result of uploading a spreadsheet for importing purposes.
The design needs to account for being in a standalone dll that is used in other projects.
I was considering the idea of using a Partial View. This would be preferable since it could make calls to the html helper to render my grid and contain the explanatory text.
However, I couldn't find examples online that really lent themselves to my scenario. So I not confident of the details.
Thanks for input in advance.
Explanatory text can be stored in a view model. It'll be stored in a
single place and it can easily point to a resource file with
localization (if needed)
Re-factoring. I can't get into more details as I haven't seen the code
If you opt-in for a partial view, you can render control with #Html.RenderPartial, #Html.EditorFor, #Html.DisplayFor depending on what kind of control this is. In my project I have controls for storing and displaying search criteria. So I have something on the lines of
#Html.EditorFor(model => model.CategorySearch, "CategorySearch")
I'm not sure about a seperate DLL, but if you have a clear seperation between a view and domain model, then you should be able to get away with copying your view model and view related components (e.g. partial view, editor/display templates etc)
I hope this helps
I'm new to MVC3 (and MVC in general) and looking for a bit of advice. Pointing me in the direction of some good articles or tutorials would be good enough I think. I'm a bit familiar with the concept of MVC, and I've been a c# programmer (hobbyist and partly professional) for a while now.
The issue I have is that I have an object (call it "Game"), which has a List<T> as a property (call T "Player"), and I want the user to "select" the player to add them to the Game.
All players would be managed in another part of the application, so there is no need to think about "managing" the master player pool at this point.
I'm looking for a best practice for:
adding custom objects to a list that of n length while on a page.
Searching for and selecting a custom object in the first place.
I can do the standard pages for the database access so that's not a problem. In asp I would have just done something like a wizard and managed everything through postback on the page, but I want to try and keep to best practice where i can for this project.
Any pointers welcome, also looking for some good physical books to buy on MVC.
If I understand you correctly you want two elements within the page, a player search (over all players) and a list of players already added to the game.
For the player search you want to use a bit of jQuery to hook up an actionResult that returns a JSON result of your player results. You can then display these results without having to leave the page, in appearance much like an AJAX post in webforms.
You have more options for how you add the player to the game, depending on if you want to add more than one at once, or want a backout stage (so you can "add" players and then cancel out and they won't be added).
the option I think would give the most seamless interface would be a jQuery/javascript call to an action method which datawise adds your player to the game, and use jQuery to add the element to your players in the game on the page.
For the adding of a player in your controller you could return a bool in a JSON result, just you have confirmation that the player was successfully added to the list.
For reference: This is quite an old article but highlights the power of working with jQuery and MVC quite nicely I think http://andreasohlund.net/2008/12/21/asp-net-mvc-jquery-true/