一、意图

  将一个类的接口转换为另一个用户希望的接口。Adapter模式使得由于接口不兼容的类可以一起工作。

二、UML

  对于类适配器，C++可以使用多继承完成，即对Target使用public继承，对Adaptee使用private继承；在其他语言中则可以选择将Adaptee作为private成员变量使用。

三、示例

#include <iostream>
#include <map>
#include <memory>

class Target
{
public:
    virtual ~Target() = default;

    virtual std::string Request() const
    {
        return "Target";
    }
};

class Adaptee
{
public:
    std::string SpecificRequest() const
    {
        return "Adaptee";
    }
};

// 类适配器
class ClassAdapter : public Target, private Adaptee
{
public:
    ClassAdapter() : Target(), Adaptee() {}

    std::string Request() const override
    {
        return "ClassAdapter + " + this->SpecificRequest();
    }
};

// 对象适配器
class ObjectAdapter : public Target
{
private:
    Adaptee* adaptee;
public:
    ObjectAdapter(Adaptee* p_adaptee) : Target()
    {
        adaptee = p_adaptee;
    }

    std::string Request() const override
    {
        return "ObjectAdapter + " + adaptee->SpecificRequest();
    }
};

void Cilent(const Target* p_target)
{
    std::cout << p_target->Request() << std::endl;
}

int main()
{
    Target* myTarget = new Target();
    Adaptee* myAdaptee = new Adaptee();
    ClassAdapter* classAdapter = new ClassAdapter();
    ObjectAdapter* objectAdapter = new ObjectAdapter(myAdaptee);

    Cilent(myTarget);
    Cilent(classAdapter);
    Cilent(objectAdapter);

    return 0;
}