PHP设计模式-解释器

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适用性

  • 理解：就是一个上下文的连接器
  • 使用场景：构建一个编译器，SQL解析器
  • 下面我们来实现一个简单增删改查的sql解析器

    代码示例

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class SqlInterpreter
{
    /**
     * 表名
     * @var string
     */
    private $_tableName = '';

    /**
     * 当前类的实例
     * @var object
     */
    private static $_instance;

    /**
     * 设置表名
     *
     * @param string $table 表名
     */
    public static function db($tableName='')
    {
        if (empty($tableName)) {
            throw new Exception("argument tableName is null", 400);
        }
        // 单例
        if(!self::$_instance instanceof self){// instanceof运算符的优先级高于！
            self::$_instance = new self();
        }
        // 更新实例表名
        self::$_instance->_setTableName($tableName);
        // 返回实例
        return self::$_instance;
    }

    /**
     * 设置表名
     *
     * @param string $tableName 表名
     */
    private function _setTableName($tableName='')
    {
        $this->_tableName = $tableName;
    }

    /**
     *  插入一条数据
     *
     * @param  array $data 数据
     * @return mixed
     */
    public function insert($data=[])
    {
        if (empty($data)) {
            throw new Exception("argument data is null", 400);
        }
        $count = count($data);
        //拼接字段
        $field = array_keys($data);
        $fieldString = '';
        foreach ($field as $k => $v) {
            if ($k === (int)($count - 1)) {
                $fieldString .= "`{$v}`";
                continue;
            }
            $fieldString .= "`{$v}`".',';
        }
        unset($k);
        unset($v);

        //拼接值
        $value = array_values($data);
        $valueString = '';
        foreach ($value as $k => $v) {
            if ($k === (int)($count - 1)) {
                $valueString .= "'{$v}'";
                continue;
            }
            $valueString .= "'{$v}'".',';
        }
        unset($k);
        unset($v);

        $sql = "INSERT INTO `{$this->_tableName}` ({$fieldString}) VALUES ({$valueString})";

        echo $sql . "\n";
    }

    /**
     *  删除数据
     *
     * @param  array $data 数据
     * @return mixed
     */
    public function delete($data=[])
    {
        if (empty($data)) {
            throw new Exception("argument data is null", 400);
        }
        // 拼接where语句
        $count = (int)count($data);
        $where = '';
        $dataCopy = $data;
        $pop = array_pop($dataCopy);
        if ($count === 1) {
            $field = array_keys($data)[0];
            $value = array_values($data)[0];
            $where = "`{$field}` = '{$value}'";
        }else{
            foreach ($data as $k => $v) {
                if ($v === $pop) {
                    $where .= "`{$k}` = '{$v}'";
                    continue;
                }
                $where .= "`{$k}` = '{$v}' AND ";
            }
        }

        $sql = "DELETE FROM `{$this->_tableName}` WHERE {$where}";

        echo $sql . "\n";
    }

    /**
     *  更新一条数据
     *
     * @param  array $data 数据
     * @return mixed
     */
    public function update($data=[])
    {
        if (empty($data)) {
            throw new Exception("argument data is null", 400);
        }
        if (empty($data['id'])) {
            throw new Exception("argument data['id'] is null", 400);
        }
        $set = '';
        $dataCopy = $data;
        $pop = array_pop($dataCopy);
        foreach ($data as $k => $v) {
            if ($v === $pop) {
                $set .= "`{$k}` = '$v'";
                continue;
            }
            $set .= "`{$k}` = '$v',";
        }

        $sql = "UPDATE `{$this->_tableName}` SET {$set}";

        echo $sql . "\n";
    }

    /**
     *  查找一条数据
     *
     * @param  array $data 数据
     * @return mixed
     */
    public function find($data=[])
    {
        if (empty($data)) {
            throw new Exception("argument data is null", 400);
        }

        // 拼接where语句
        $count = (int)count($data);
        $where = '';
        $dataCopy = $data;
        $pop = array_pop($dataCopy);
        if ($count === 1) {
            $field = array_keys($data)[0];
            $value = array_values($data)[0];
            $where = "`{$field}` = '{$value}'";
        }else{
            foreach ($data as $k => $v) {
                if ($v === $pop) {
                    $where .= "`{$k}` = '{$v}'";
                    continue;
                }
                $where .= "`{$k}` = '{$v}' AND ";
            }
        }

        $sql = "SELECT * FROM `{$this->_tableName}` WHERE {$where}";

        echo $sql . "\n";
    }
}


try {
    //增加数据
    SqlInterpreter::db('user')->insert([
        'nickname' => 'tigerb',
        'mobile'   => '1366666666',
        'password' => '123456'
    ]);
    //删除数据
    SqlInterpreter::db('user')->delete([
        'nickname' => 'tigerb',
        'mobile'   => '1366666666',
    ]);
    //修改数据
    SqlInterpreter::db('member')->update([
        'id'       => '1',
        'nickname' => 'tigerbcode'
    ]);
    //查询数据
    SqlInterpreter::db('member')->find([
        'mobile'   => '1366666666',
    ]);
} catch (\Exception $e) {
    echo 'error:' . $e->getMessage();
}