What is combination mode? (for example)

Composite Pattern

Composite Pattern: Allows customers to combine objects into a tree structure to express "whole/ section" hierarchy. Compositions enable clients to work with individual objects as well as combinations of objects in a consistent manner.

The combination mode allows us to create a structure of objects in a tree shape, which contains combinations and individual objects. Using composition structures, we can apply the same operations to compositions and individual objects. In other words, in most cases we can ignore the difference between combinations of objects and individual objects.

Components that contain other components are composite objects; components that do not contain other components are leaf node objects.

In order to maintain "transparency", the composition model often violates the single responsibility principle. In other words, on the one hand, it must manage internal objects, and on the other hand, it must provide a set of access interfaces.

When the combined mode interface provides a method for deleting child nodes, it will be easier to implement the deletion operation if there is a pointer to the parent node in the component.

Take the combat effectiveness calculation of an army as an example to demonstrate the combination mode

The army is composed of infantry, artillery, and special forces. They all have the ability to fight and have their own combat effectiveness. . We combine them into an army and complete the calculation of combat effectiveness.

<?php
//抽象士兵类
interface soldier{
public function fire();
}
//步兵 攻击力5
class bubing implements soldier{
public function fire(){
return 5;
}
}
//炮兵 攻击力8
class paobing implements soldier{
public function fire(){
return 8;
}
}
//特种兵 攻击力 12
class tezhongbing implements soldier{
public function fire(){
return 12;
}
}
//军队类实现兵种的组合
class arm{
//存储作战兵种的数组 
private $soldier = array();
//添加作战兵种
public function add($soldierType){
//获取对应的兵种对象
$soldier  = new $soldierType();
//保存进数组利用数组的键记录兵种 便于删除
$this->soldier[$soldierType] = $soldier;
}
//删除兵种
public function delete($soldierType){
if(isset($this->soldier[$soldierType])){
unset($this->soldier[$soldierType]);
}
}
//计算并输出战斗能力
public function show(){
$zhantouli = 0;
foreach($this->soldier as $v){
$zhantouli += $v->fire();
}
echo "军队的战斗力: ".$zhantouli;
}
}
$arm = new arm();
$arm->add(&#39;bubing&#39;);
$arm->add(&#39;paobing&#39;);
$arm->show();
$arm->delete(&#39;paobing&#39;);
$arm->show();

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