2.5 隐藏委托关系

【1】源代码

#include <QString>

class Department;
class Person
{
public:
    QString getName()
    {
        return m_name;
    }
    void setName(QString name)
    {
        m_name = name;
    }

    Department* get_department()
    {
        return m_department; // 获取部门对象
    }

    void set_department(Department *department)
    {
        m_department = department;
    }

private:
    QString m_name;
    Department *m_department;
};

class Department
{
public:
    QString getCode()
    {
        return m_code;
    }
    void setCode(QString code)
    {
        m_code = code;
    }
    Person get_manager()
    {
        return m_manager; // 获取经理人
    }
    void set_manager(Person manager)
    {
        m_manager = manager;
    }

private:
    QString m_code;
    Person m_manager;
};

int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);

    Person person;
    QString strName = person.get_department()->get_manager().getName(); // 客户端
    // 这样的编码对客户暴露了Department的工作原理，于是客户知道:Department用以追踪"经理"这条信息。

    return a.exec();
}

【2】隐藏委托关系

class Person
{
public:
    // 如果对客户隐藏Department，可以减少耦合。为了到达预期的目的，在Person中建立一个简单的委托函数。
    Person getManager()
    {
        return m_department->get_manager(); // 隐藏委托类
    }

    QString getName()
    {
        return m_name;
    }
    void setName(QString name)
    {
        m_name = name;
    }

    Department* get_department()
    {
        return m_department; // 获取部门对象
    }

    void set_department(Department *department)
    {
        m_department = department;
    }

private:
    QString m_name;
    Department *m_department;
};

class Department
{
public:
    QString getCode()
    {
        return m_code;
    }
    void setCode(QString code)
    {
        m_code = code;
    }
    Person get_manager()
    {
        return m_manager; // 获取经理人
    }
    void set_manager(Person manager)
    {
        m_manager = manager;
    }

private:
    QString m_code;
    Person m_manager;
};

int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);

    Person person;
    QString strName = person.getManager().getName(); // 客户端调用方式

    return a.exec();
}

【3】总结

客户通过一个委托类来调用另一个对象。

在服务类上建立客户所需的所有函数，用以隐藏委托关系。

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