怎样用C++实现组合模式 树形结构处理统一对象的方法

#include <iostream>
#include <vector>
#include <string>
#include <memory> // For std::shared_ptr

// Component (组件) 抽象基类
class Component {
public:
    virtual ~Component() = default; // 虚析构函数确保正确释放资源
    virtual void operation() = 0;   // 所有组件都必须实现的核心操作

    // 管理子组件的方法。对于叶子节点，这些方法通常是空操作或抛出异常。
    virtual void add(std::shared_ptr<Component> component) {
        // 默认实现为空，由Composite重写
        std::cerr << "Warning: Cannot add component to a Leaf node or unsupported component." << std::endl;
    }
    virtual void remove(std::shared_ptr<Component> component) {
        // 默认实现为空，由Composite重写
        std::cerr << "Warning: Cannot remove component from a Leaf node or unsupported component." << std::endl;
    }
    // 实际项目中可能还需要 getChild(int index) 等方法
};

// Leaf (叶子) 类
class Leaf : public Component {
private:
    std::string name_;
public:
    Leaf(const std::string& name) : name_(name) {}

    void operation() override {
        std::cout << "Leaf [" << name_ << "] performs its specific operation." << std::endl;
    }
    // Leaf节点不会有子节点，所以add/remove方法沿用基类的默认空实现或可重写抛出异常。
};

// Composite (组合节点) 类
class Composite : public Component {
private:
    std::vector<std::shared_ptr<Component>> children_; // 存储子组件的集合
    std::string name_;
public:
    Composite(const std::string& name) : name_(name) {}

    void operation() override {
        std::cout << "Composite [" << name_ << "] performing its operation. Delegating to children:" << std::endl;
        for (const auto& child : children_) {
            child->operation(); // 递归调用子组件的操作
        }
    }

    void add(std::shared_ptr<Component> component) override {
        children_.push_back(component);
        std::cout << "  Added component to Composite [" << name_ << "]." << std::endl;
    }

    void remove(std::shared_ptr<Component> component) override {
        // 在实际应用中，移除操作可能需要更复杂的逻辑，比如根据指针值或唯一ID查找并移除
        // 这里的实现仅作示意，实际移除需要迭代查找
        auto it = std::remove(children_.begin(), children_.end(), component);
        if (it != children_.end()) {
            children_.erase(it, children_.end());
            std::cout << "  Removed component from Composite [" << name_ << "]." << std::endl;
        } else {
            std::cerr << "  Warning: Component not found in Composite [" << name_ << "] for removal." << std::endl;
        }
    }
};

if-else

if (isLeaf) { ... } else { ... }

Composite

Component

std::shared_ptr

shared_ptr

std::unique_ptr

shared_ptr

std::weak_ptr

add/remove