Yii学习笔记（二）

数据库的使用

Yii 内置多种数据库支持，如： SQLite，MySQL，PostregSQL，MSSQL 或 Oracle 数据库。

创建数据库

CREATE TABLE `country` (
  `code` CHAR(2) NOT NULL PRIMARY KEY,
  `name` CHAR(52) NOT NULL,
  `population` INT(11) NOT NULL DEFAULT '0'
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

INSERT INTO `country` VALUES ('AU','Australia',18886000);
INSERT INTO `country` VALUES ('BR','Brazil',170115000);
INSERT INTO `country` VALUES ('CA','Canada',1147000);
INSERT INTO `country` VALUES ('CN','China',1277558000);
INSERT INTO `country` VALUES ('DE','Germany',82164700);
INSERT INTO `country` VALUES ('FR','France',59225700);
INSERT INTO `country` VALUES ('GB','United Kingdom',59623400);
INSERT INTO `country` VALUES ('IN','India',1013662000);
INSERT INTO `country` VALUES ('RU','Russia',146934000);
INSERT INTO `country` VALUES ('US','United States',278357000);

CREATE TABLE `country` (

`code` CHAR(2) NOT NULL PRIMARY KEY,

`name` CHAR(52) NOT NULL,

`population` INT(11) NOT NULL DEFAULT '0'

) ENGINE=InnoDB DEFAULT CHARSET=utf8;

INSERT INTO `country` VALUES ('AU','Australia',18886000);

INSERT INTO `country` VALUES ('BR','Brazil',170115000);

INSERT INTO `country` VALUES ('CA','Canada',1147000);

INSERT INTO `country` VALUES ('CN','China',1277558000);

INSERT INTO `country` VALUES ('DE','Germany',82164700);

INSERT INTO `country` VALUES ('FR','France',59225700);

INSERT INTO `country` VALUES ('GB','United Kingdom',59623400);

INSERT INTO `country` VALUES ('IN','India',1013662000);

INSERT INTO `country` VALUES ('RU','Russia',146934000);

INSERT INTO `country` VALUES ('US','United States',278357000);

配置数据库连接

需要确保已经安装了 PHP PDO 扩展和你所使用的数据库的 PDO 驱动（例如 MySQL 的 pdo_mysql）

pdo_mysql

编辑 config/db.php配置文件，来修改相应的配置信息。而这个数据库

<?php

return [
    'class' => 'yii\db\Connection',
    'dsn' => 'mysql:host=localhost;dbname=yii2basic',
    'username' => 'root',
    'password' => '',
    'charset' => 'utf8',
];

<?php

return [

'class' => 'yii\db\Connection',

'dsn' => 'mysql:host=localhost;dbname=yii2basic',

'username' => 'root',

'password' => '',

'charset' => 'utf8',

];

创建活动记录

创建 models/Country.php 文件，文件内容：

<?php

namespace app\models;

use yii\db\ActiveRecord;

class Country extends ActiveRecord
{

}

<?php

namespace app\models;

use yii\db\ActiveRecord;

class Country extends ActiveRecord

{

}

Country 类只需继承 yii\db\ActiveRecord，Yii 就能根据类名去猜测对应的数据表名。如果类名和数据表名不能直接对应，可以覆写 yii\db\ActiveRecord::tableName()方法去显式指定相关表名。

操作表数据

use app\models\Country;

// 获取 country 表的所有行并以 name 排序
$countries = Country::find()->orderBy('name')->all();

// 获取主键为 “US” 的行
$country = Country::findOne('US');

// 输出 “United States”
echo $country->name;

// 修改 name 为 “U.S.A.” 并在数据库中保存更改
$country->name = 'U.S.A.';
$country->save();

use app\models\Country;

// 获取 country 表的所有行并以 name 排序

$countries = Country::find()->orderBy('name')->all();

// 获取主键为 “US” 的行

$country = Country::findOne('US');

// 输出 “United States”

echo $country->name;

// 修改 name 为 “U.S.A.” 并在数据库中保存更改

$country->name = 'U.S.A.';

$country->save();

创建操作

之前是在在 site 控制器中创建操作，在这里为所有和国家有关的数据新建一个控制器更加合理。新控制器名为 CountryController，保存在controllers/CountryController.php中，并在其中创建一个 index 操作，如下：

<?php

namespace app\controllers;

use yii\web\Controller;
use yii\data\Pagination;
use app\models\Country;

class CountryController extends Controller
{
    public function actionIndex()
    {
        $query = Country::find();

        $pagination = new Pagination([
            'defaultPageSize' => 5,
            'totalCount' => $query->count(),
        ]);

        $countries = $query->orderBy('name')
            ->offset($pagination->offset)
            ->limit($pagination->limit)
            ->all();

        return $this->render('index', [
            'countries' => $countries,
            'pagination' => $pagination,
        ]);
    }
}

<?php

namespace app\controllers;

use yii\web\Controller;

use yii\data\Pagination;

use app\models\Country;

class CountryController extends Controller

{

public function actionIndex()

{

$query = Country::find();

$pagination = new Pagination([

'defaultPageSize' => 5,

'totalCount' => $query->count(),

]);

$countries = $query->orderBy('name')

->offset($pagination->offset)

->limit($pagination->limit)

->all();

return $this->render('index', [

'countries' => $countries,

'pagination' => $pagination,

]);

}

创建视图

在 views 目录下先创建一个名为 country 的子目录。
这个目录存储所有由 country 控制器渲染的视图。在 views/country 目录下创建一个名为 index.php 的视图文件，内容如下：

<?php
use yii\helpers\Html;
use yii\widgets\LinkPager;
?>
 <h1>Countries</h1>
 <ul>
<?php foreach ($countries as $country): ?>
    <li>
        <?= Html::encode("{$country->name} ({$country->code})") ?>:
        <?= $country->population ?>
    </li>
<?php endforeach; ?>
</ul>

<?= LinkPager::widget(['pagination' => $pagination]) ?>

<?php

use yii\helpers\Html;

use yii\widgets\LinkPager;

<h1>Countries</h1>

<ul>

<?php foreach ($countries as $country): ?>

<li>

<?= Html::encode("{$country->name} ({$country->code})") ?>:

<?= $country->population ?>

</li>

<?php endforeach; ?>

</ul>

<?= LinkPager::widget(['pagination' => $pagination]) ?>

yii\data\Pagination 接收到 URL 中的 page 参数把当前的页码设为 2。新的数据库请求将会以 LIMIT 5 OFFSET 5 查询并显示。

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