什么是Ruby on Rails中的MVC？[英] What is MVC in Ruby on Rails?

问题描述

Could someone please explain MVC to me in Ruby on Rails, in layman terms. I am especially interested in understanding the Model in MVC (can't get my head around the model).

推荐答案

Some background, MVC is a (compound) design pattern and was developed in 1979 by Trygve Reenskaug (Smalltalk).

True MVC was primarily planned for use in n-tier (non web) systems and it splits a system into 3 distinct parts, a Model, View and Controller

The Model

• Contains data for the application (often linked to a database)
• Contains state of the application (e.g. what orders a customer has)
• Contains all business logic
• Notifies the View of state changes (** not true of ROR, see below)
• No knowledge of user interfaces, so it can be reused

The View

• Generates the user interface which presents data to the user
• Passive, i.e. doesn’t do any processing
• Views work is done once the data is displayed to the user.
• Many views can access the same model for different reasons

The Controller

• Receive events from the outside world (usually through views)
• Interact with the model
• Displays the appropriate view to the user

** Classic MVC is not suited to web applications, as the model cannot send all changes to the view in an observer fashion (the view is a web page). The Model2 was introduced to overcome the changing infrastructure by JSP team in 90s . MVC Web frameworks are really not MVC, but Model2 (this is true of Ruby on Rails).

Here is a description of GUI patterns including MVC from the master, Martin Fowler GUI Architectures

The best book I have found so far is Agile Web Development with Rails. It begins by assuming no knowledge, and is quite comprehensive.

Hope this helps to shed some light for you!

其他推荐答案

MVC basically indicates Model-View-Controller. And MVC used by many languages like PHP, Perl, Python etc. Generally MVC works like this:

Request first comes to the controller, controller finds and appropriate view and interacts with model, model interacts with your database and send the response to controller then controller based on the response give the output parameter to view.

其他推荐答案

Your Model is the data structure that your program uses.

The View is the part that interacts with the screen or the next level up.

The Controller generally processes data between the model and view

MVC structures are often nested, so a "Model" or "View" may contain its own MVC (Think of a component on the screen. You may just fill it with a string, but behind the scenes the code of the component draws its own little view, has it's own little model (the string you pass in) and has a little controller drawing the data onto the view.

In Rails, the roles of the model, view and controller are well-defined by the framework, any tutorial will point out the three components as it walks you through the files it created.

In other systems, those pieces may be harder to identify. Also, MVC is not "Perfect", just keep in mind that there are valid alternatives, but it's a good way to start organizing.