This helps in data access which you can call from the controllers. In a well-implemented MVC architecture, the models normally host the bulk of the business logic because this logic is closely coupled to data manipulation and models are responsible for that data level. Utilizing models to their full capacity encourages lean controllers, controllers that are more focused on connecting the models to the views and vice-versa than actually implementing business logic. Although we used Sails as an example of an MVC framework to see how to use the model in MVC to its full potentials, these principles are framework agnostic and should apply to your chosen MVC framework of choice.
Here are the key takeaways:. Reply 0. Kelvin Omereshone Follow Kelvin is an independent software maker currently building Sailscasts, a platform to learn server-side JavaScript. He is also a technical writer and works as a Node. We made a custom demo for. No really. Click here to check it out.
In my opinion, a model should just contain properties and almost no functionality so there are as few methods in model classes as possible. My collegue though believes that models could and should have more than that and offer a lot more functionality.
Let's say we wanted to create a blog. A blog has articles and tags. Each article can have multiple tags and each tag can belong to multiple articles. So we have a m:n relation here.
Now, assume that we're working loose coupled here which means that it could happen that we have an instance of Article which has no Tags yet so we'll use an Ajax call to our backend which has a database containing all the information to get the tags that belong to our article. Here comes the tricky part. My collegue believes that this breaks with the idea of MVC, he suggests that the model should take care about this:. And outside of the model you'd do: blog.
However, as handy as this might be I believe that this approach breaks with MVC because at the end of the day all models will be full of methods that do various funky stuff and the controller and helper classes do almost nothing. In my understanding of MVC, models should only contain properties and a minimum of "helper methods" inside. For example a model "Article" could offer a method getNumOfTags but it shouldn't do any Ajax calls on its own. Generally I try to keep controllers simple in terms of logic too.
If business logic is required, it will go up to 'service layer' classes to handle it. I just keep models purely as entity objects. You should stop treating "model" in MVC like some class. Model is not a class or object. Model is a layer in modern MVC, there has been some evolutions since the inception of concept. What people tend to call "models" are actually domain object I blame Rails for this mass-stupidity. The application logic interaction between domain logic structures and storage abstraction should be a part of model layer.
To be more precise: it should be inside the Services. The interaction between presentation layer models, views, layouts, templates and model layer should happen only through those services. Application has no place in controllers. Controllers are structures of presentation layer, and they are responsible for handling user input. Please do not expose deomain objects to it. Handy tricks are nice, why not use them were you can? That being said, as you've pointed out, you may get bloated models if you put all sorts of logic in them.
Likewise, though, you can get bloated controllers when they do massive amounts in each action. There are ways to abstract elements out of either, if that's necessary too. At the end of the day all design patterns are is guidelines. You shouldn't blindly follow any rule, just because someone else said it. Do what works for you, what you think gives clean, extensible code and hits whatever metrics you think make good code. All that being said, for true idealistic MVC I would say that models should not have any external actions, they're data representations, nothing more.
But feel free to disagree Your suggestion about the modules without any business logic inside sounds more like you talk about Value Objects. The suggestion of your college sounds more like Domain Objects. In my opinion the concept which will be used depends on the framework which is used that's the practical view, the more philosophical one is bellow.
If framework is used it usually sets rules about how you should implement each component. For example we can look at different MVC frameworks.
In Flex's Cairngorm framework we have both. VO Value objects are primary used for bindings to the view, while the DO Domain objects hold the business logic. If we look at ASP. Backbone's documentation says:. Models are the heart of any JavaScript application, containing the interactive data as well as a large part of the logic surrounding it: conversions, validations, computed properties, and access control.
If we look into the traditional MVC provided by Smalltalk we see that: "Model: manages the behavior and data of the application domain" so we have some behavior in it, not just plain data. Let's think practically, if don't have any logic in the Model probably we should put all the application and business logic into the Controller. Now let's focus on a concrete example. Imagine we have a model which is a Graph. We want to find the shortest path between two nodes in it. A good question is where to put the algorithm which finds the shortest path?
Use the EF Core Migrations feature to create the database. Migrations is a set of tools that create and update a database to match the data model. The InitialCreate argument is the migration name. Any name can be used, but by convention, a name is selected that describes the migration. Because this is the first migration, the generated class contains code to create the database schema.
The database schema is based on the model specified in the MvcMovieContext class. Update-Database : Updates the database to the latest migration, which the previous command created. No type was specified for the decimal column 'Price' on entity type 'Movie'. This will cause values to be silently truncated if they do not fit in the default precision and scale. Net CLI. If you get an exception similar to the following, you may have missed the migrations step :.
You may not be able to enter decimal commas in the Price field. To support jQuery validation for non-English locales that use a comma "," for a decimal point and for non US-English date formats, the app must be globalized. For globalization instructions, see this GitHub issue.
With EF Core, data access is performed using a model. A model is made up of entity classes and a context object that represents a session with the database. The context object allows querying and saving data. The database context is derived from Microsoft.
DbContext and specifies the entities to include in the data model. Services, such as the database context, are registered with DI in Program. These services are provided to components that require them via constructor parameters.
The database context is used in each of the CRUD methods in the controller. The ASP. For local development, the ASP. The constructor uses Dependency Injection to inject the database context MvcMovieContext into the controller.
Earlier in this tutorial, you saw how a controller can pass data or objects to a view using the ViewData dictionary. The ViewData dictionary is a dynamic object that provides a convenient late-bound way to pass information to a view. MVC provides the ability to pass strongly typed model objects to a view. This strongly typed approach enables compile time code checking. The scaffolding mechanism passed a strongly typed model in the MoviesController class and views.
The id parameter is generally passed as route data. The id parameter is defined as a nullable type int? A lambda expression is passed in to the FirstOrDefaultAsync method to select movie entities that match the route data or query string value. If a movie is found, an instance of the Movie model is passed to the Details view:. The model statement at the top of the view file specifies the type of object that the view expects.
When the movie controller was created, the following model statement was included:. This model directive allows access to the movie that the controller passed to the view. The Model object is strongly typed. For example, in the Details. The Create and Edit methods and views also pass a Movie model object. Examine the Index.
Notice how the code creates a List object when it calls the View method. The code passes this Movies list from the Index action method to the view:. When the movies controller was created, scaffolding included the following model statement at the top of the Index. The model directive allows access to the list of movies that the controller passed to the view by using a Model object that's strongly typed.
For example, in the Index. Among other benefits, the compiler validates the types used in the code. For example, the following project file uses version 5. NET and the listed NuGet packages:. The Select Projects dialog displays, with the MvcMovie project selected. Select the Ok button. A License Acceptance dialog displays. Review the licenses, then select the Accept button. The preceding command adds the aspnet-codegenerator scaffolding tool. When SQLite is selected, the template generated code is ready for development.
Migrations are a set of tools that create and update a database to match the data model. Services, such as the database context, must be registered with DI in Startup. Components that require these services are provided via constructor parameters. Logging configuration is commonly provided by the Logging section of appsettings.
To log SQL statements, add "Microsoft. Command": "Information" to the appsettings.
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