流接口模式（Fluent Interface）

目的

用来编写易于阅读的代码，就像自然语言一样（如英语）

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：CDbCommand 与 CActiveRecord 也使用此模式

UML 图

K6NHRBLVHw.png

代码

你可以在 GitHub 上找到这些代码

Sql.php

  2. <?php
  4. namespace DesignPatterns\Structural\FluentInterface;
  6. class Sql
  7. {
  8.     /**
  9.      * @var array
  10.      */
  11.     private $fields = [];
  13.     /**
  14.      * @var array
  15.      */
  16.     private $from = [];
  18.     /**
  19.      * @var array
  20.      */
  21.     private $where = [];
  23.     public function select(array $fields): Sql
  24.     {
  25.         $this->fields = $fields;
  27.         return $this;
  28.     }
  30.     public function from(string $table, string $alias): Sql
  31.     {
  32.         $this->from[] = $table.' AS '.$alias;
  34.         return $this;
  35.     }
  37.     public function where(string $condition): Sql
  38.     {
  39.         $this->where[] = $condition;
  41.         return $this;
  42.     }
  44.     public function __toString(): string
  45.     {
  46.         return sprintf(
  47.             'SELECT %s FROM %s WHERE %s',
  48.             join(', ', $this->fields),
  49.             join(', ', $this->from),
  50.             join(' AND ', $this->where)
  51.         );
  52.     }
  53. }

测试

Tests/FluentInterfaceTest.php

  2. <?php
  4. namespace DesignPatterns\Structural\FluentInterface\Tests;
  6. use DesignPatterns\Structural\FluentInterface\Sql;
  7. use PHPUnit\Framework\TestCase;
  9. class FluentInterfaceTest extends TestCase
  10. {
  11.     public function testBuildSQL()
  12.     {
  13.         $query = (new Sql())
  14.                 ->select(['foo', 'bar'])
  15.                 ->from('foobar', 'f')
  16.                 ->where('f.bar = ?');
  18.         $this->assertEquals('SELECT foo, bar FROM foobar AS f WHERE f.bar = ?', (string) $query);
  19.     }
  20. }