How is mvvm different from mvc

Nowadays we have many options when it comes to architecture design patterns. For easier to understand, we can use a simple example like developing a screen to search books in the BookSearch App. The aim of these architectures is to separate the responsibilities of visualizing, processing, and data management for UI applications.

Their goals are to increase. Or MVC for short is a widely used design pattern for architecting software apps. The pattern was originally designed by Trygve Reenskaug during his time working on Smalltalk where it was initially called Model-View-Controller-Editor.

The pattern breaks an app up into three components. This pattern based on MVC and MVP which attempts to more clearly separate the development of UI from that of the business logic and behavior in an application.

As an example, ASP. NET and WordPress projects tend to fall under this category. It keeps track of its own internal state, i. As an example, React and Angular projects tend to fall under this category. Writing code in comment? Please use ide. Load Comments. What's New. Most popular in Android. Most visited in Difference Between. We use cookies to ensure you have the best browsing experience on our website. That's it, at least for the purpose of this comparison.

Let's retain one feature of this web stuff, not as it is today, but as it existed ten years ago, when JavaScript was a lowly, despicable annoyance, which real programmers did well to steer clear of: The HTML page is essentially dumb and passive.

The browser is a thin client, or if you will, a poor client. There is no intelligence in the browser. Full page reloads rule. The »view« is generated anew each time around. Let's remember that this web way, despite being all the rage, was horribly backward compared to the desktop.

Desktop apps are fat clients, or rich clients, if you will. Even a program like Microsoft Word can be thought of as some kind of client, a client for documents. They're clients full of intelligence, full of knowledge about their data. They're stateful. They cache data they're handling in memory. No such crap as a full page reload.

And this rich desktop way is probably where the second acronym originated, MVVM. Don't be fooled by the letters, by the omission of the C. Controllers are still there. They need to be. Nothing gets removed. We just add one thing: statefulness, data cached on the client and along with it intelligence to handle that data.

That data, essentially a cache on the client, now gets called »ViewModel«. It's what allows rich interactivity. And that's it. Browsers can no longer be legitimately called thin clients. Look at their programmability. Look at their memory consumption. Look at all the Javascript interactivity on modern web pages.

Personally, I find this theory and acronym business easier to understand by looking at what it's referring to in concrete reality. Abstract concepts are useful, especially when demonstrated on concrete matter, so understanding may come full circle. The controller is replaced with a ViewModel. The ViewModel sits below the UI layer.

The ViewModel exposes the data and command objects that the view needs. You could think of this as a container object that view goes to get its data and actions from. The ViewModel pulls its data from the model. This article outlines some of the facets of the two. In the Model-View-ViewModel design pattern, an app is composed of three general components. Model : This represents the data model that your app consumes.

For example, in a picture sharing app, this layer might represent the set of pictures available on a device and the API used to read and write to the picture library. View : An app typically is composed of multiple pages of UI. Each page shown to the user is a view in MVVM terminology. The view is the XAML code used to define and style what the user sees. For example, in a picture sharing app, the views would be the UI that show the user the list of albums on the device, the pictures in an album, and perhaps another that shows the user a particular picture.

It contains the logic with which to manage the data from the model and exposes the data as a set of properties to which the XAML UI, or views, can bind. For example, in a picture sharing app, the ViewModel would expose a list of albums, and for each album expose a list of pictures. The UI is agnostic of where the pictures come from and how they are retrieved. It simply knows of a set of pictures as exposed by the ViewModel and shows them to the user.

If I'm not full of junk, I'm surprised no one has created a hybrid, where your VM is merely a M proxy, and C provides all functionality. In a controlled environment you should have less code and a common source of logic; which should always live within the controller. However; in the web world MVC easily gets divided into view creation logic and view dynamic logic.

Creation lives on the server and dynamic lives on the client. You see this a lot with ASP. The client will then interact with the View in which case AngularJS steps in to as a local controller.

Once submitted the Model or a new Model is passed back to the server controller and handled. Thus the cycle continues and there are a lot of other translations of this handling when working with sockets or AJAX etc but over all the architecture is identical. MVVM is a reactive environment meaning you typically write code such as triggers that will activate based on some event.

It is not MS specific. The ViewModel fires usually a property changed event and the View reacts to it based on whatever triggers you create. This can get technical but the bottom line is the View is stateless and without logic.

It simply changes state based on values. Furthermore, ViewModels are stateless with very little logic, and Models are the State with essentially Zero logic as they should only maintain state. Based on the Model the controller will modify the View. Views are usually tied to Controllers with Interfaces so that the Controller can work with a variety of Views.

In ASP. People will argue and get this confused with application MVC and try to do both at which point maintaining the project will eventually become a disaster. Let the Controller change the View. An example of this is submitting a username and password. Whether desktop or web page on client the Controller should handle the submit process whenever the View fires the Submit action. If done correctly you can always find your way around an MVC web or local app easily.

MVVM is personally my favorite as it's completely reactive. If a Model changes state the ViewModel listens and translates that state and that's it!!! The View is then listening to the ViewModel for state change and it also updates based on the translation from the ViewModel.

Here's a slight example: Let's say the you want to have a menu slide in on a button press. The Controller will know when you click the Menu button and then tell the View to slide in the Menu based on another Interface method such as SlideMenuIn. A round trip for what reason?

Incase the Controller decides you can't or wants to do something else instead that's why. The Controller should be in charge of the View with the View doing nothing unless the Controller says so.

When designing a ViewModel you should never assume a View will have any features at all and just pass translated model state. So how would you manage the Menu? When the data makes sense that's how. So, one way to do this is to give the Menu a list of options probably an array of inner ViewModels.

If that list has data, the Menu then knows to open via the trigger, if not then it knows to hide via the trigger. You simply have data for the menu or not in the ViewModel. This way the View is completely reactive and generic and can be used in many different situations. All of this probably makes absolutely no sense if you're not already at least slightly familiar with the architecture of each and learning it can be very confusing as you'll find ALOT OF BAD information on the net.

If you do MVC, which is great, then make sure you Controller is manageable and in full control of your View.

If you have a large View consider adding controls to the View that have different Controllers. Very frustrating to maintain. Take a moment and design things separately in a way that will work as separate components And always let the Controller tell the Model to commit or persist storage.

Do not use interfaces for one. Let your View decide how it's going to look based on values. Play with the View with Mock data. If you end up having a View that is showing you a Menu as per the example even though you didn't want it at the time then GOOD. You're view is working as it should and reacting based on the values as it should. Just add a few more requirements to your trigger to make sure this doesn't happen when the ViewModel is in a particular translated state or command the ViewModel to empty this state.

Remember you can't assume there is a menu or not in the ViewModel. And finally, the Model should just allow you to change and most likely store state. This is where validation and all will occur; for example, if the Model can't modify the state then it will simply flag itself as dirty or something. When the ViewModel realizes this it will translate what's dirty, and the View will then realize this and show some information via another trigger.

All data in the View can be binded to the ViewModel so everything can be dynamic only the Model and ViewModel has absolutely no idea about how the View will react to the binding. As a matter of fact the Model has no idea of a ViewModel either.

The View should not see a model period. I give a rats crack what demo you've seen or how you've done it, that's wrong. Here's my final tip One will have more control with limited to zero flexibility while the other will have no control and unlimited flexibility.