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流接口模式(Fluent Interface)#

1. 目的#

用来编写易于阅读的代码,就像自然语言一样(如英语)

2. 例子#

  • Doctrine2 的 QueryBuilder,就像下面例子中类似
  • PHPUnit 使用连贯接口来创建 mock 对象
  • Yii 框架:CDbCommandCActiveRecord 也使用此模式

3. UML 图#

4. 代码#

你可以在 GitHub 上找到这些代码

Sql.php

<?php

namespace DesignPatterns\Structural\FluentInterface;

class Sql
{
    /**
     * @var array
     */
    private $fields = [];

    /**
     * @var array
     */
    private $from = [];

    /**
     * @var array
     */
    private $where = [];

    public function select(array $fields): Sql
    {
        $this->fields = $fields;

        return $this;
    }

    public function from(string $table, string $alias): Sql
    {
        $this->from[] = $table.' AS '.$alias;

        return $this;
    }

    public function where(string $condition): Sql
    {
        $this->where[] = $condition;

        return $this;
    }

    public function __toString(): string
    {
        return sprintf(
            'SELECT %s FROM %s WHERE %s',
            join(', ', $this->fields),
            join(', ', $this->from),
            join(' AND ', $this->where)
        );
    }
}

5. 测试#

Tests/FluentInterfaceTest.php

<?php

namespace DesignPatterns\Structural\FluentInterface\Tests;

use DesignPatterns\Structural\FluentInterface\Sql;
use PHPUnit\Framework\TestCase;

class FluentInterfaceTest extends TestCase
{
    public function testBuildSQL()
    {
        $query = (new Sql())
                ->select(['foo', 'bar'])
                ->from('foobar', 'f')
                ->where('f.bar = ?');

        $this->assertEquals('SELECT foo, bar FROM foobar AS f WHERE f.bar = ?', (string) $query);
    }
}

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