构建自己的PHP框架--实现Model类(1)

在之前的博客中，我们定义了ORM的接口，以及决定了使用PDO去实现。最后我们提到会有一个Model类实现ModelInterface接口。

现在我们来实现这个接口，如下：

<?php
namespace sf\db;

use PDO;

/**
* Model is the base class for data models.
* @author Harry Sun <sunguangjun@126.com>
*/
class Model implements ModelInterface
{
/**
* Declares the name of the database table associated with this Model class.
* @return string the table name
*/
public static function tableName()
{
return get_called_class();
}

/**
* Returns the primary key **name(s)** for this Model class.
* @return string[] the primary key name(s) for this Model class.
*/
public static function primaryKey()
{
return ['id'];
}

/**
* Returns a single model instance by a primary key or an array of column values.
*
* ```php
* // find the first customer whose age is 30 and whose status is 1
* $customer = Customer::findOne(['age' => 30, 'status' => 1]);
* ```
*
* @param mixed $condition a set of column values
* @return static|null Model instance matching the condition, or null if nothing matches.
*/
public static function findOne($condition)
{

}

/**
* Returns a list of models that match the specified primary key value(s) or a set of column values.
*
*  ```php
* // find customers whose age is 30 and whose status is 1
* $customers = Customer::findAll(['age' => 30, 'status' => 1]);
* ```
*
* @param mixed $condition a set of column values
* @return array an array of Model instance, or an empty array if nothing matches.
*/
public static function findAll($condition)
{

}

/**
* Updates models using the provided attribute values and conditions.
* For example, to change the status to be 2 for all customers whose status is 1:
*
* ~~~
* Customer::updateAll(['status' => 1], ['status' => '2']);
* ~~~
*
* @param array $attributes attribute values (name-value pairs) to be saved for the model.
* @param array $condition the condition that matches the models that should get updated.
* An empty condition will match all models.
* @return integer the number of rows updated
*/
public static function updateAll($condition, $attributes)
{

}

/**
* Deletes models using the provided conditions.
* WARNING: If you do not specify any condition, this method will delete ALL rows in the table.
*
* For example, to delete all customers whose status is 3:
*
* ~~~
* Customer::deleteAll([status = 3]);
* ~~~
*
* @param array $condition the condition that matches the models that should get deleted.
* An empty condition will match all models.
* @return integer the number of rows deleted
*/
public static function deleteAll($condition)
{

}

/**
* Inserts the model into the database using the attribute values of this record.
*
* Usage example:
*
* ```php
* $customer = new Customer;
* $customer->name = $name;
* $customer->email = $email;
* $customer->insert();
* ```
*
* @return boolean whether the model is inserted successfully.
*/
public function insert()
{

}

/**
* Saves the changes to this model into the database.
*
* Usage example:
*
* ```php
* $customer = Customer::findOne(['id' => $id]);
* $customer->name = $name;
* $customer->email = $email;
* $customer->update();
* ```
*
* @return integer|boolean the number of rows affected.
* Note that it is possible that the number of rows affected is 0, even though the
* update execution is successful.
*/
public function update()
{

}

/**
* Deletes the model from the database.
*
* @return integer|boolean the number of rows deleted.
* Note that it is possible that the number of rows deleted is 0, even though the deletion execution is successful.
*/
public function delete()
{

}
}

当然现在里面还没有写任何的实现，只是继承了ModelInterface接口。

现在我们先来实现一下findOne方法，在开始实现之前我们要想，我们所有的model都要基于PDO，所以我们应该在model中有一个PDO的实例。所以我们需要在Model类中添加如下变量和方法。

/**
* @var $pdo PDO instance
*/
public static $pdo;

/**
* Get pdo instance
* @return PDO
*/
public static function getDb()
{
if (empty(static::$pdo)) {
$host = 'localhost';
$database = 'sf';
$username = 'jun';
$password = 'jun';
static::$pdo = new PDO("mysql:host=$host;dbname=$database", $username, $password);
static::$pdo->exec("set names 'utf8'");
}

return static::$pdo;
}

用static变量可以保证所有继承该Model的类用的都是同一个PDO实例，getDb方法实现了单例模式（其中的配置暂时hard在这里，在之后的博客里会抽出来），保证了一个请求中，使用getDb只会取到一个PDO实例。

下面我们来实现findOne方法，我们现在定义的findOne有很多局限，例如不支持or，不支持select部分字段，不支持表关联等等。我们之后会慢慢完善这一些内容。其实findOne的实现就是拼接sql语句去执行，直接来看下代码：

public static function findOne($condition)
{
//  拼接默认的前半段sql语句
$sql = 'select * from ' . static::tableName() . ' where ';
// 取出condition中value作为参数
$params = array_values($condition);
$keys = [];
foreach ($condition as $key => $value) {
array_push($keys, "$key = ?");
}
// 拼接sql完成
$sql .= implode(' and ', $keys);
$stmt = static::getDb()->prepare($sql);
$rs = $stmt->execute($params);

if ($rs) {
$row = $stmt->fetch(PDO::FETCH_ASSOC);
if (!empty($row)) {
// 创建相应model的实例
$model = new static();
foreach ($row as $rowKey => $rowValue) {
// 给model的属性赋值
$model->$rowKey = $rowValue;
}
return $model;
}
}
// 默认返回null
return null;
}

我们需要来验证一下我们的代码是正确的，先在MySQL中设置一下用户及权限，mock一下数据。

相应的SQL语句如下：

/*创建新用户*/
CREATE USER jun@localhost IDENTIFIED BY 'jun';

/*用户授权 授权jun用户拥有sf数据库的所有权限*/
GRANT ALL PRIVILEGES ON sf.* TO jun@'%' IDENTIFIED BY 'jun';

/*刷新授权*/
FLUSH PRIVILEGES;

/*创建数据库*/
CREATE DATABASE IF NOT EXISTS `sf`;

/*选择数据库*/
USE `sf`;

/*创建表*/
CREATE TABLE IF NOT EXISTS `user` (
id INT(20) NOT NULL AUTO_INCREMENT,
name VARCHAR(50),
age INT(11),
PRIMARY KEY(id)
);

/*插入测试数据*/
INSERT INTO `user` (name, age) VALUES('harry', 20), ('tony', 23), ('tom', 24);

然后再在models文件夹中创建一个User.php，代码如下：

<?php
namespace app\models;

use sf\db\Model;

/**
* User model
* @property integer $id
* @property string $name
* @property integer $age
*/
class User extends Model
{
public static function tableName()
{
return 'user';
}
}

最后只剩在Controller中使用findOne验证一下了。修改SiteController.php的actionTest方法如下：

public function actionTest()
{
$user = User::findOne(['age' => 20, 'name' => 'harry']);
$data = [
'first' => 'awesome-php-zh_CN',
'second' => 'simple-framework',
'user' => $user
];
echo $this->toJson($data);
}

打出的如下结果：

{"first":"awesome-php-zh_CN","second":"simple-framework","user":{"id":"1","name":"harry","age":"20"}}

如果将findOne中的条件改成['age' => 20, 'name' => 'tom']，返回值就变为如下结果：

{"first":"awesome-php-zh_CN","second":"simple-framework","user":null}

好了，今天就先到这里。项目内容和博客内容也都会放到Github上，欢迎大家提建议。

code：https://github.com/CraryPrimitiveMan/simple-framework/tree/0.5

blog project：https://github.com/CraryPrimitiveMan/create-your-own-php-framework