简介

建造者模式可将对象的初始化转变成一步步配置的过程。如当对象的初始化时有很多可选参数，建造者模式能够定制参数实现对象的创立。益处有：

  1. 定制对象参数
  2. 针对不同参数，做不同的校验，如当设置了三角形的两个边长，设置第三个边时必须满足两边之和大于第三边的条件。

角色

  • Builder 类

    定义建造一个Product分几个步骤

  • 具体 Builder 类

    实现不同的步骤

  • Director

    属于疾速建造某一种产品的办法，如 Director 提供了创立自动挡和手动挡汽车两种办法，创立自动挡汽车中其实是调用 setA setB，而创立主动单汽车中调用setC setD。也能够不应用 Director，间接应用 Builder 的 setA setB 去设置属性

  • 要被实例化的类

    初始化时可定制的参数较多，如 setA setB setC...

类图

图中的 Director 在 make 办法中封装了设置产品属性的步骤，通过传入不同的 builder 类，实现不同的实现步骤，创立不同的产品。

代码

interface Builder{    public function producePartA(): void;    public function producePartB(): void;    public function producePartC(): void;}class ConcreteBuilder1 implements Builder{    private $product;    public function __construct()    {        $this->reset();    }    public function reset(): void    {        $this->product = new Product1();    }    public function producePartA(): void    {        $this->product->parts[] = "PartA1";    }    public function producePartB(): void    {        $this->product->parts[] = "PartB1";    }    public function producePartC(): void    {        $this->product->parts[] = "PartC1";    }    public function getProduct(): Product1    {        $result = $this->product;        $this->reset();        return $result;    }}/** * EN: It makes sense to use the Builder pattern only when your products are * quite complex and require extensive configuration. * * Unlike in other creational patterns, different concrete builders can produce * unrelated products. In other words, results of various builders may not * always follow the same interface. * * RU:       ,   *       . * *      ,    *    .  ,   *          . */class Product1{    public $parts = [];    public function listParts(): void    {        echo "Product parts: " . implode(', ', $this->parts) . "\n\n";    }}class Director{    private $builder;    public function setBuilder(Builder $builder): void    {        $this->builder = $builder;    }    public function buildMinimalViableProduct(): void    {        $this->builder->producePartA();    }    public function buildFullFeaturedProduct(): void    {        $this->builder->producePartA();        $this->builder->producePartB();        $this->builder->producePartC();    }}function clientCode(Director $director){    $builder = new ConcreteBuilder1();    $director->setBuilder($builder);    echo "Standard basic product:\n";    $director->buildMinimalViableProduct();    $builder->getProduct()->listParts();    echo "Standard full featured product:\n";    $director->buildFullFeaturedProduct();    $builder->getProduct()->listParts();    // 不应用 Director，间接操作 builder 来创立产品    echo "Custom product:\n";    $builder->producePartA();    $builder->producePartC();    $builder->getProduct()->listParts();}$director = new Director();clientCode($director);

output:

Standard basic product:Product parts: PartA1Standard full featured product:Product parts: PartA1, PartB1, PartC1Custom product:Product parts: PartA1, PartC1