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53 lines
2.8 KiB
Markdown
53 lines
2.8 KiB
Markdown
MVC Overview
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============
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Yii implements the model-view-controller (MVC) design pattern, which is
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widely adopted in Web programming. MVC aims to separate business logic from
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user interface considerations, so that developers can more easily change
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each part without affecting the other. In MVC, the model represents the
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information (the data) and the business rules; the view contains elements
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of the user interface such as text, form inputs; and the controller manages
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the communication between the model and the view.
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Besides implementing MVC, Yii also introduces a front-controller, called
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`Application`, which encapsulates the execution context for the processing
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of a request. Application collects information about a user request and
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then dispatches it to an appropriate controller for further handling.
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The following diagram shows the static structure of a Yii application:
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A Typical Workflow
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------------------
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The following diagram shows a typical workflow of a Yii application when
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it is handling a user request:
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1. A user makes a request with the URL `http://www.example.com/index.php?r=post/show&id=1`
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and the Web server handles the request by executing the bootstrap script `index.php`.
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2. The bootstrap script creates an [Application](/doc/guide/basics.application)
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instance and runs it.
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3. The Application obtains detailed user request information from
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an [application component](/doc/guide/basics.application#application-component)
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named `request`.
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4. The application determines the requested [controller](/doc/guide/basics.controller)
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and [action](/doc/guide/basics.controller#action) with the help
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of an application component named `urlManager`. For this example, the controller
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is `post`, which refers to the `PostController` class; and the action is `show`,
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whose actual meaning is determined by the controller.
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5. The application creates an instance of the requested controller
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to further handle the user request. The controller determines that the action
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`show` refers to a method named `actionShow` in the controller class. It then
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creates and executes filters (e.g. access control, benchmarking) associated
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with this action. The action is executed if it is allowed by the filters.
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6. The action reads a `Post` [model](/doc/guide/basics.model) whose ID is `1` from the database.
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7. The action renders a [view](/doc/guide/basics.view) named `show` with the `Post` model.
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8. The view reads and displays the attributes of the `Post` model.
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9. The view executes some [widgets](/doc/guide/basics.view#widget).
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10. The view rendering result is embedded in a [layout](/doc/guide/basics.view#layout).
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11. The action completes the view rendering and displays the result to the user.
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