面向对象的设计在C ++ - 装饰与未知类型的子的父对象(OO design in C++ - D

我目前的工作中哪些对象沿着贝塞尔曲线动画的系统上。在所定义的各种用户，指出在曲线上，可以存在其中动画对象具有到反应的事件。这可能是速度的变化，变化的动画例程，面临方向等的变化......

到目前为止，我有以下AnimationEvent类。

class AnimationEvent
{
private:
    unsigned int    m_eventID;

    float   m_InteroplationPoint;

    float   m_SpeedInMPS;

public:
    AnimationEvent(unsigned int id, float interpolationPoint);
    ~AnimationEvent(void);

    const unsigned int getEventID();
    void setInterpolationPoint(float interpPoint);
    const float getInterpPoint();

    const float getSpeed();
};

每个事件被指定为沿曲线的对象，并在达到其内插点时，曲线类调用getSpeed()以改变当前的动画速度的功能。

我真正想要做的是实现一个系统，如与装饰设计模式，该事件可以与多个对象进行装饰，并达到时，所有的装饰将被应用。我遇到的问题是，我不能一个指针传递给父对象的孩子，因为这会再创建一个循环依赖，但我也有这个问题，我不知道（在编译）什么类型的行动该事件将被装饰。

如何克服这种任何想法，将不胜感激！如果我忘了任何信息，这可能会帮助，我会尝试和编辑。

Answer 1:

你可以申请一个装饰状的图案这个问题，如果你愿意让已经发生的对象，以前的所有事件的轨道。所有你需要做的是每个事件存储在某种类型的载体。然后，你可以做任何类型的，你想操作的。

#include <iostream>
#include <vector>
using namespace std;

class Animatee;
class AnimateEvent
{
public:
    virtual Animatee & perform(Animatee & on) = 0;
};

class Animatee
{
public:
    Animatee() : value(0){};

    void addEvent(AnimateEvent * event)
    {
        if(event != NULL)
        {
            events.push_back(event);
        }

    }

    Animatee & act()
    {
        for(vector<AnimateEvent * >::iterator it = events.begin(); it != events.end();++it)
        {
            AnimateEvent * event = *it;
            event->perform(*this);
        }

        return *this;
    }

    double value;   //don't do this, but something more encap'ed
private:

    vector<AnimateEvent * > events;
};

class Add : public AnimateEvent
{
    virtual Animatee & perform(Animatee & on)
    {
        on.value = on.value + 1;
        return on;
    }
};

class Subtract : public AnimateEvent
{
    virtual Animatee & perform(Animatee & on)
    {
        on.value = on.value - 1;
        return on;
    }
};

class Multiply : public AnimateEvent
{
    virtual Animatee & perform(Animatee & on)
    {
        on.value = on.value * 2;
        return on;
    }
};

class Div : public AnimateEvent
{
    virtual Animatee & perform(Animatee & on)
    {
        on.value = on.value / 2.0;
        return on;
    }
};

int main() {
    Animatee matee;
    matee.addEvent(new Add());

    //cout << "Before: " << matee.value << " After: " << matee.act().value << endl; <~~~ Undefined btw, acting on the object twice in one "statement"
    double before = matee.value;
    cout << "Before: " << before << " After: " << matee.act().value << endl;

    matee.addEvent(new Subtract());
    before = matee.value;
    cout << "Before: " << before << " After: " << matee.act().value << endl;

    matee.addEvent(new Subtract());
    before = matee.value;
    cout << "Before: " << before << " After: " << matee.act().value << endl;

    matee.addEvent(new Add());
    matee.addEvent(new Add());
    matee.addEvent(new Add());
    before = matee.value;
    cout << "Before: " << before << " After: " << matee.act().value << endl;

    matee.addEvent(new Multiply());
    before = matee.value;
    cout << "Before: " << before << " After: " << matee.act().value << endl;

    before = matee.value;
    cout << "Before: " << before << " After: " << matee.act().value << endl;

    return 0;
}