关于后端:结构型设计模式组合对象树-Composite

简介

组合模式又叫对象树，将对象依照树形构造串起来，呈现出部分和整体雷同的个性。

树中每个节点都由两局部组成，首先节点有本人的业务数据，其次节点内能够含有子节点汇合。

比方盒子中能够放物品，也能够放其余小盒子，小盒子里又能够放物品和其余更小的盒子。

当计算盒子的物品价格时，只须要将盒子里自身的物品价格，加上小盒子里所有物品价格即可，递归解决。

角色

• 形象节点 Component

  定义一个节点的根底办法，如外部增加子节点等

• 具体节点之叶子节点 Leaf

  叶子节点没有子节点

• 具体节点之非叶子节点 Composite/Container

  非叶子节点，可增加子节点

或者也能够不辨别是否是叶子节点，都视为节点即可

类图

图中显示，Leaf 和 Composite 都实现 Component 接口。

Composite 可增加或删除子节点，execute 则指派调用子节点的 execute 办法。

Leaf 的 execute 是真正执行逻辑的中央

代码

<?phpabstract class Component{    protected $parent;    public function setParent(Component $parent)    {        $this->parent = $parent;    }    public function getParent(): Component    {        return $this->parent;    }    public function add(Component $component): void { }    public function remove(Component $component): void { }    public function isComposite(): bool    {        return false;    }    abstract public function operation(): string;}class Leaf extends Component{    public function operation(): string    {        return "Leaf";    }}class Composite extends Component{    protected $children;    public function __construct()    {        $this->children = new \SplObjectStorage();    }    public function add(Component $component): void    {        $this->children->attach($component);        $component->setParent($this);    }    public function remove(Component $component): void    {        $this->children->detach($component);        $component->setParent(null);    }    public function isComposite(): bool    {        return true;    }    public function operation(): string    {        $results = [];        foreach ($this->children as $child) {            $results[] = $child->operation();        }        return "Branch(" . implode("+", $results) . ")";    }}function clientCode(Component $component){    echo "RESULT: " . $component->operation();}// 只有一个叶子节点$simple = new Leaf();echo "Client: I've got a simple component:\n";clientCode($simple);echo "\n";// 构建一个tree$tree = new Composite();$branch1 = new Composite();$branch1->add(new Leaf());$branch1->add(new Leaf());$branch2 = new Composite();$branch2->add(new Leaf());$tree->add($branch1);$tree->add($branch2);echo "Client: Now I've got a composite tree:\n";clientCode($tree);// 合并两个treefunction clientCode2(Component $component1, Component $component2){    if ($component1->isComposite()) {        $component1->add($component2);    }    echo "RESULT: " . $component1->operation();}echo "\n";echo "Client: I don't need to check the components classes even when managing the tree:\n";clientCode2($tree, $simple);

output:

Client: I've got a simple component:RESULT: LeafClient: Now I've got a composite tree:RESULT: Branch(Branch(Leaf+Leaf)+Branch(Leaf))Client: I don't need to check the components classes even when managing the tree:RESULT: Branch(Branch(Leaf+Leaf)+Branch(Leaf)+Leaf)

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