OOP在C ++中这样做的方法？ [英] OOPs way to do this in C++?
问题描述
我想在运行时更改类的方法。我正在制作一款游戏，并希望NPC对象根据游戏设计师采用不同的方法。那个
是，他们可能会决定这个暴徒应该能够飞行，是为了战斗，等等......而不是一堆开关声明或者
if..else我觉得能够在课堂上插入
函数/方法会很好。
嗯，这是旧的C方式，我在这里做过，但我对它不满意
。原因如下：
1.我必须为每个函数交朋友
2.我必须分配一个函数指针，那里可能会出错，加上
维持这是一种痛苦
3.这不是，IMO，它是最好的方式，但我不知道/>
更好的方式。
我只是在这里展示了这个动作的功能，但实际上会有一个运动之一的
一个用于战斗，一个用于防护（如果它是一个警卫），
等......
有关如何改进设计的任何建议？
#include< iostream>
#include< string>
class Base
{
朋友void Walk（Base& base）;
朋友void Fly（Base& base）;
朋友无效游泳（基地和基地）;
朋友无效浮动（基地和基地）;
公共：
基地（int X，const std :: string Movement）：X（X），Move_（NULL）
{
if（Movement ==" Flies" ）
Move_ = Fly;
else if（Movement ==Walks）
Move_ = Walk;
else if（Movement ==" Swims"）
Move_ = Swim;
else if（Movement ==" Floats"）
Move_ = Float;
else
Move_ =步行;
}
void Move （）{if（Move_！= NULL）{Move_（* this）; } $
私人：
无效（*移动_）（基础&）;
int X;
};
void Walk（Base& base）
{
base.X + = 5;
std :: cout<< 走到 << base.X<< " \ n";
}
void Fly（Base& base）
{
base.X + = 7;
std :: cout<< 飞到 << base.X<< " \ n";
}
无效游泳（基地和基地）
{
base.X + = 3;
std :: cout<< 游到 << base.X<< " \ n";
}
void Float（Base& base）
{
base.X + = 2;
std :: cout<< 浮动到 << base.X<< " \ n";
}
int main（）
{
Base MyBase（10，Flies）;
MyBase.Move（）;
std :: string wait;
std :: getline（std :: cin，wait）;
}
问候，
Jim Langston
4月10日下午2:55，Jim Langston < tazmas ... @ rocketmail.comwrote：
我想在运行时更改类的方法。
尝试考虑：
http://en.wikipedia.org/wiki/Double_dispatch
http://en.wikipedia.org/wiki/Visitor_pattern
谢谢，
4月10日下午3:40，aiooua < aio ... @ gmail.comwrote：
4月10日下午2:55，Jim Langston < tazmas ... @ rocketmail.comwrote：
我想在运行时更改类的方法。
尝试考虑：
http://en.wikipedia.org/wiki/Double_dispatch
http://en.wikipedia.org/wiki/Visitor_pattern
Jim Langston写道：
有关如何改进的建议设计？
正如aiouua所说，正确答案是使用装饰模式。
无论如何，我想指出即使你的设计你不需要
任何朋友的功能。考虑一下：
#include< iostream>
#include< string>
#include< functional>
等级基础
{
私人：
无效行走（）;
void Fly（）;
void Swim（）;
void Float（）;
public：
Base（int X，const std :: string Movement）：Move_（NULL），X（X）
{
if （运动==飞行）
Move_ = std :: mem_fun_ref（& Base :: Fly）;
else if（Movement ==" Walks" ）
Move_ = std :: mem_fun_ref（& Base :: Walk）;
else if（Movement ==" Swims"）
Move_ = std :: mem_fun_ref（& Base :: Swim）;
else if（Movement ==" Floats"）
Move_ = std :: mem_fun_ref（ & Base :: Float）;
else
Move_ = std :: mem_fun_ref（& Base :: Walk）;
}
void Move（）{Move _（* this）; }
私人：
std :: mem_fun_ref_t< void，BaseMove_;
int X;
};
void Base :: Walk（）
{
X + = 5;
std :: cout<< 走到 << X << " \ n";
}
void Base :: Fly（）
{
X + = 7;
std :: cout<< 飞到 << X << " \ n";
}
void Base :: Swim（）
{
X + = 3;
std :: cout<< 游到 << X << " \ n";
}
void Base :: Float（）
{
X + = 2;
std :: cout<< 浮动到 << X << " \ n";
}
int main（）
{
Base MyBase（10，Flies）;
MyBase.Move（）;
std :: string wait;
std :: getline（std :: cin，wait）;
返回0;
}
如前所述，它;更好的装饰，有一个基础与
虚拟Move（）= 0;
和每个派生类实现不同的Move（ ）。
问候，
Zeppe
I want to change a class''s methods at run time. I''m making a game and want
NPC objects to have different methods depending on a game designer. That
is, they may decide that this mob should be able to fly for movement, be
agressivie for combat, etc... Rather than a bunch of switch statements or
if..else I was thinking it would be good to be able to plug in
functions/methods to the class.
Well, there''s the old C way, which I''ve done here, but am not happy with it
at all. For a few reasons:
1. I have to friend every function
2. I have to assign a function pointer, and things can go wrong there, plus
it gets to be a pain to maintain
3. It''s just not, IMO, the best way it could be, but I don''t know of a
better way.
I''ve only shown the function here for movement, but in reality there would
be one for movement, one for combat, one for guarding (if it''s a guard),
etc...
Any suggestions on how to improve the design?
#include <iostream>
#include <string>
class Base
{
friend void Walk( Base& base );
friend void Fly( Base& base );
friend void Swim( Base& base );
friend void Float( Base& base );
public:
Base( int X, const std::string Movement ): X(X), Move_( NULL )
{
if ( Movement == "Flies" )
Move_ = Fly;
else if ( Movement == "Walks" )
Move_ = Walk;
else if ( Movement == "Swims" )
Move_ = Swim;
else if ( Movement == "Floats" )
Move_ = Float;
else
Move_ = Walk;
}
void Move() { if ( Move_ != NULL ) { Move_( *this ); } }
private:
void (*Move_)( Base& );
int X;
};
void Walk( Base& base )
{
base.X += 5;
std::cout << "Walked to " << base.X << "\n";
}
void Fly( Base& base )
{
base.X += 7;
std::cout << "Flew to " << base.X << "\n";
}
void Swim( Base& base )
{
base.X += 3;
std::cout << "Swam to " << base.X << "\n";
}
void Float( Base& base )
{
base.X += 2;
std::cout << "Floated to " << base.X << "\n";
}
int main()
{
Base MyBase( 10, "Flies" );
MyBase.Move();
std::string wait;
std::getline( std::cin, wait );
}
Regards,
Jim Langston
On Apr 10, 2:55 pm, "Jim Langston" <tazmas...@rocketmail.comwrote:I want to change a class''s methods at run time.try considering:
http://en.wikipedia.org/wiki/Double_dispatch
http://en.wikipedia.org/wiki/Visitor_pattern
thanks,
On Apr 10, 3:40 pm, "aiooua" <aio...@gmail.comwrote:On Apr 10, 2:55 pm, "Jim Langston" <tazmas...@rocketmail.comwrote:I want to change a class''s methods at run time.try considering:
http://en.wikipedia.org/wiki/Double_dispatch
http://en.wikipedia.org/wiki/Visitor_patternand probably a more relevant:
http://en.wikipedia.org/wiki/Decorator_pattern
thanks,
Jim Langston wrote:
Any suggestions on how to improve the design?The correct answer, as aiouua said, is to use the decorator pattern.
Anyway, I wanted to point out that even with your design you don''t need
any friend function. Consider this:
#include <iostream>
#include <string>
#include <functional>
class Base
{
private:
void Walk();
void Fly();
void Swim();
void Float();
public:
Base( int X, const std::string Movement ): Move_( NULL ), X(X)
{
if ( Movement == "Flies" )
Move_ = std::mem_fun_ref(&Base::Fly);
else if ( Movement == "Walks" )
Move_ = std::mem_fun_ref(&Base::Walk);
else if ( Movement == "Swims" )
Move_ = std::mem_fun_ref(&Base::Swim);
else if ( Movement == "Floats" )
Move_ = std::mem_fun_ref(&Base::Float);
else
Move_ = std::mem_fun_ref(&Base::Walk);
}
void Move() { Move_(*this); }
private:
std::mem_fun_ref_t<void, BaseMove_;
int X;
};
void Base::Walk()
{
X += 5;
std::cout << "Walked to " << X << "\n";
}
void Base::Fly()
{
X += 7;
std::cout << "Flew to " << X << "\n";
}
void Base::Swim()
{
X += 3;
std::cout << "Swam to " << X << "\n";
}
void Base::Float()
{
X += 2;
std::cout << "Floated to " << X << "\n";
}
int main()
{
Base MyBase( 10, "Flies" );
MyBase.Move();
std::string wait;
std::getline( std::cin, wait );
return 0;
}
As already said, it;s better to decorate, having a Base with
virtual Move() = 0;
and each derived class implement a different Move().
Regards,
Zeppe
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