在Yii 中，模型用於處理數(shù)據(jù)邏輯、驗證輸入、表示數(shù)據(jù)庫表結(jié)構(gòu)並支持業(yè)務(wù)邏輯及非數(shù)據(jù)庫表單。 1. 模型通過rules() 方法定義驗證規(guī)則，確保用戶輸入符合要求；2. 使用Active Record 類映射數(shù)據(jù)庫表，實現(xiàn)數(shù)據(jù)的增刪改查操作；3. 可添加如isSubscribed() 等業(yè)務(wù)方法及TimestampBehavior 等行為擴展功能；4. 支持不依賴數(shù)據(jù)庫的表單模型，適用於聯(lián)繫表單、搜索表單等場景，提升代碼組織性和可維護性。

In Yii, models are the components responsible for handling data logic and representing the structure of your application's data. They're a core part of the MVC (Model-View-Controller) architecture that Yii follows. The main purpose of models is to manage data, validate user input, and interact with the database — but they can also be used for other data-related tasks like formatting or business logic.

What Do Models Typically Handle?

A model in Yii usually corresponds to a single table or structure in your database. It handles things like:

• Retrieving and saving data
• Validating form inputs
• Defining rules and behaviors
• Managing relationships between different data types

This keeps your controllers clean and focused on request handling, not data manipulation.

1. Handling Data Validation and Input

One of the most common uses of models in Yii is validating user input. For example, when you have a form for creating a new user, the model defines what fields are required, what formats they should follow, and any custom validation rules.

Here's how it typically works:

• You define validation rules inside the rules() method of your model.
• When a form is submitted, Yii automatically checks these rules before saving data.
• If validation fails, errors are returned so users can correct their input.

 public function rules()
{
    return [
        [['username', 'email', 'password'], 'required'],
        ['email', 'email'],
        ['username', 'string', 'max' => 255],
    ];
}

This helps centralize validation logic and ensures consistent behavior across your app.

2. Representing Database Tables

Models often represent a specific table in the database. In Yii, this is usually done using Active Record classes, which extend yii\db\ActiveRecord .

Each model class is tied to a specific table through the tableName() method:

 public static function tableName()
{
    return 'user';
}

Once set up, you can perform operations like:

• Fetching records: User::findOne($id)
• Saving changes: $user->save()
• Deleting records: $user->delete()

This makes working with databases much more intuitive and object-oriented.

3. Adding Business Logic and Custom Behaviors

Beyond just storing and retrieving data, models are a great place to put business logic. For instance, if a user has a subscription, you might add a method like isSubscribed() directly in the User model.

You can also attach behaviors to models — such as timestamps, soft deletes, or audit trails — using Yii's behavior system. This keeps your code modular and reusable.

For example, adding automatic timestamps:

 public function behaviors()
{
    return [
        'timestamp' => [
            'class' => 'yii\behaviors\TimestampBehavior',
            'value' => new \yii\db\Expression('NOW()'),
        ],
    ];
}

This way, you don't have to manually update created/updated times every time.

4. Supporting Form Models Without Databases

Not all models need to connect to a database. Yii also supports form models — sometimes called "model-only" or "standalone" models — which are useful for forms that don't map directly to a table.

These models still use the same validation features but don't inherit from ActiveRecord . Instead, they extend yii\base\Model .

Use cases include:

• Contact forms
• Search forms
• Settings configuration forms

They're especially helpful when you want to collect and validate data that isn't stored directly in the database.

So, models in Yii play a key role in managing data flow and logic. Whether you're dealing with database records, complex validation, or standalone forms, putting that logic into models keeps your code organized and maintainable. Basically, they're where your data lives — and where you make sure it behaves properly.

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