数据库之AR Active Record (AR) 是一个流行的 对象-关系映射 (ORM) 技术。 每个 AR 类代表一个数据表（或视图），数据表（或视图）的列在 AR 类中体现为类的属性，一个 AR 实例则表示表中的一行。 – yiichina 数据库之AR gii CRUD C C实现原理 R R实现原理
Active Record (AR) 是一个流行的 对象-关系映射 (ORM) 技术。 每个 AR 类代表一个数据表（或视图），数据表（或视图）的列在 AR 类中体现为类的属性，一个 AR 实例则表示表中的一行。
– yiichina
这里简单提一下gii 具体百度一下，你就知道
是YII的代码生成工具
下面使用的User类就是gii生成的
<code><span>public</span> <span><span>function</span> <span>actionCreate</span><span>()</span>
{</span>
<span>//$user = new User; //实例化userModel</span>
<span>//或</span>
<span>//$user = User::model();</span>
<span>//$user->setIsNewRecord(true);</span>
<span>//给对应的字段赋值</span>
<span>$user</span>->username = <span>"框架"</span>;
<span>$user</span>->status = <span>0</span>;
<span>$user</span>->city = <span>5</span>;
<span>//插入数据</span>
<span>//这里值得细说的是 IsNewRecord变量为true</span>
<span>//场景(scenario)为insert </span>
<span>//具体看 实现原理</span>
<span>if</span>(<span>$user</span>->save())
{
<span>echo</span> <span>'插入成功'</span>;
}<span>else</span>
{
var_dump(<span>$user</span>->errors);
}
}</code>实例化 User model
<code><span>$user</span> = <span>new</span> User;</code>
User extends CActiveRecord 调用 CActiveRecord的构造方法
<code><span>public</span> function __construct(<span>$scenario</span><span>=</span><span>'insert'</span>)
{
<span>//使用 静态方法 model实例化对象 场景(scenario)为空</span>
<span>if</span>(<span>$scenario</span><span>===</span><span>null</span>) <span>// internally used by populateRecord() and model()</span>
<span>return</span>;
<span>$this</span><span>-></span>setScenario(<span>$scenario</span>); <span>//设置场景为 insert</span>
<span>$this</span><span>-></span>setIsNewRecord(<span>true</span>); <span>//设置 这个一条新纪录</span>
<span>//获得字段的默认值</span>
<span>$this</span><span>-></span>_attributes<span>=</span><span>$this</span><span>-></span>getMetaData()<span>-></span>attributeDefaults;
<span>$this</span><span>-></span>init(); <span>//一个空方法 子类可以自己重写</span>
<span>$this</span><span>-></span>attachBehaviors(<span>$this</span><span>-></span>behaviors()); <span>//绑定行为</span>
<span>$this</span><span>-></span>afterConstruct(); <span>//触发 构造结束事件</span>
}</code><code><span>public</span> <span><span>function</span> <span>actionRead</span><span>()</span>
{</span>
<span>$user</span> = User::model()->find();
<span>//这里的场景(Scenario)仍然是update哦</span>
<span>$user</span> = User::model()->find(<span>'id = :id'</span>,<span>array</span>(<span>':id'</span>=><span>5</span>));
var_dump(<span>$user</span>);
}
<span>public</span> <span><span>function</span> <span>actionReadAll</span><span>()</span>
{</span>
<span>$user</span> = User::model()->findAll();
<span>$user</span> = User::model()->findAll(<span>'id > :lid and id ,<span>array</span>(<span>':lid'</span>=><span>5</span>,<span>':mid'</span>=><span>10</span>));
var_dump(<span>$user</span>);
}
<span>public</span> <span><span>function</span> <span>actionReadCriteria</span><span>()</span>
{</span>
<span>$criteria</span> = <span>new</span> CDbCriteria();
<span>// $criteria->addCondition('id > :lid');</span>
<span>// $criteria->addCondition('id
<span>// $criteria->addBetweenCondition('id', 5, 10); //包含 5 和 10</span>
<span>// $criteria->addInCondition('id',array(4,5,6)); </span>
<span>// $criteria->params = array(':lid'=>5,':mid'=>10);</span>
<span>$criteria</span>->addSearchCondition(<span>'username'</span>, <span>'g%'</span> ,<span>false</span>);
<span>$criteria</span>->addSearchCondition(<span>'username'</span>, <span>'g'</span>);
<span>$criteria</span>->order = <span>'id desc'</span>;
<span>// $criteria->limit = 2;</span>
<span>// $criteria->offset = 1;</span>
<span>$user</span> = User::model()->findAll(<span>$criteria</span>);
var_dump(<span>$user</span>);
}</span></span></code>find()和findall()
<code><span>//创建一个 条件对象 CDbCriteria类</span>
<span>$criteria</span>=<span>$this</span>->getCommandBuilder()
->createCriteria(<span>$condition</span>,<span>$params</span>);
<span>//查询</span>
<span>return</span> <span>$this</span>->query(<span>$criteria</span>,<span>true</span>);</code><code><span>public</span> <span><span>function</span> <span>actionUpdate</span><span>()</span>
{</span>
<span>$id</span> = Yii::app()->request->getParam(<span>'id'</span>);
<span>$user</span> = User::model()->findByPk(<span>$id</span>);
<span>$user</span>->username = <span>"被我改了吧"</span>;
<span>//这里值得细说的是 IsNewRecord变量为false</span>
<span>//场景(scenario)为update</span>
<span>//具体看 实现原理</span>
<span>if</span>(<span>$user</span>->save())
{
<span>echo</span> <span>'修改成功'</span>;
}<span>else</span>
{
var_dump(<span>$user</span>->errors);
}
}</code><code><span>$user</span> = User::model()->findByPk(<span>$id</span>);</code>
调用的User的 静态方法model
<code><span>public</span> <span>static</span> <span><span>function</span> <span>model</span><span>(<span>$className</span>=__CLASS__)</span>
{</span>
<span>return</span> <span>parent</span>::model(<span>$className</span>);
}</code>调用父类 CActiveRecord 类的 model方法
<code><span>public</span> <span>static</span> <span><span>function</span> <span>model</span><span>(<span>$className</span>=__CLASS__)</span>
{</span>
<span>if</span>(<span>isset</span>(<span>self</span>::<span>$_models</span>[<span>$className</span>]))
<span>return</span> <span>self</span>::<span>$_models</span>[<span>$className</span>];
<span>else</span>
{
<span>//实例化类</span>
<span>$model</span>=<span>self</span>::<span>$_models</span>[<span>$className</span>]=<span>new</span> <span>$className</span>(<span>null</span>);
<span>//绑定行为</span>
<span>$model</span>->attachBehaviors(<span>$model</span>->behaviors());
<span>return</span> <span>$model</span>;
}
}</code><code><span>public</span> <span><span>function</span> <span>actionDelete</span><span>()</span>
{</span>
<span>$id</span> = Yii::app()->request->getParam(<span>'id'</span>);
<span>$user</span> = User::model()->findByPk(<span>$id</span>);
<span>if</span>(<span>$user</span>->delete())
{
<span>echo</span> <span>'删除成功'</span>;
} <span>else</span> {
var_dump(<span>$user</span>->errors);
}
}</code>没有什么特别的
<code><span>if</span>(<span>!</span><span>$this</span><span>-></span>getIsNewRecord())
{
Yii<span>::trace</span>(get_class(<span>$this</span>)<span>.</span><span>'.delete()'</span>,<span>'system.db.ar.CActiveRecord'</span>);
<span>if</span>(<span>$this</span><span>-></span>beforeDelete())
{
<span>$result</span><span>=</span><span>$this</span><span>-></span>deleteByPk(<span>$this</span><span>-></span>getPrimaryKey())<span>></span><span>0</span>;
<span>$this</span><span>-></span>afterDelete();
<span>return</span> <span>$result</span>;
}
<span>else</span>
<span>return</span> <span>false</span>;
}</code>场景(scenario)
新纪录(IsNewRecord)
1.场景的作用更多体现在 insert 和 update上，这也是默认的场景只有insert和update
new User() 场景被赋值成insert
User::model() 在 query()的时候 调用 populateRecords()赋值成update
节选自yiichina网友的一片博文，比较好的描述了yii中场景的作用
2.新纪录一般用来区别insert和其他操作
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