![](/img/trans.png)
[英]C++ Factory Pattern with Smart Pointers - can't get past “use of deleted function” error
[英]Using Smart Pointers with Factory Pattern
我正在尝试在工厂设计模式中使用智能指针。 我进行了一次Google搜索,以获取一些想法,但是找不到任何实现方法,但是有很多很棒的想法。 因此,我编写了自己的代码,但是我不确定两点。
首先,我将添加代码,然后提出问题。
// AgentGameStyleFactory.hpp
#ifndef AgentGameStyleFactory_hpp
#define AgentGameStyleFactory_hpp
#include "AgentGameStyle.hpp"
#include <memory>
class AgentGameStyleFactory
{
public:
static std::unique_ptr<AgentGameStyle> instantiate(const AgentPlayingStyleData::ePLAYING_CHARACTER pStyle);
private:
static AgentGameStyle* instantiateHelper(const AgentPlayingStyleData::ePLAYING_CHARACTER pStyle);
};
#endif /* AgentGameStyleFactory_hpp */
// AgentGameStyleFactory.cpp
#include "AgentGameStyleFactory.hpp"
using namespace AgentPlayingStyleData;
std::unique_ptr<AgentGameStyle> AgentGameStyleFactory::instantiate(const ePLAYING_CHARACTER pStyle)
{
std::unique_ptr<AgentGameStyle> newStyle( instantiateHelper(pStyle) );
return std::move(newStyle);
}
AgentGameStyle* AgentGameStyleFactory::instantiateHelper(const ePLAYING_CHARACTER pStyle)
{
AgentGameStyle* newStyle = NULL;
switch(pStyle)
{
case ePLAYING_CHARACTER::ePC_CONTAIN:
newStyle = new ContainGameStyleAgent();
break;
case ePLAYING_CHARACTER::ePC_COUNTER:
newStyle = new CounterGameStyleAgent();
break;
case ePLAYING_CHARACTER::ePC_STANDARD:
newStyle = new StandardGameStyleAgent();
break;
case ePLAYING_CHARACTER::ePC_ATTACKING:
newStyle = new AttackGameStyleAgent();
case ePLAYING_CHARACTER::ePC_OVERLOAD:
newStyle = new OverloadGameStyleAgent();
break;
default:
newStyle = new StandardGameStyleAgent();
break;
}
return newStyle;
}
如您所见,我正在工厂中创建相关样式,然后将其返回并分配为
mPlayingCharacteristic = AgentGameStyleFactory::instantiate(pPlayingCharacteristic);
其中mPlayingCharacteristic
是std::unique_ptr<AgentGameStyle>
我的第一个问题是关于返回unique_ptr
。 根据我读过的帖子,这似乎是正确的,但是编译器(Xcode)给我"Moving a local object in a return statement prevents copy elision"
警告。 这是正常现象,我应该期待的事物还是这里有问题?
我的第二个问题是我是否正确std::unique_ptr<AgentGameStyle> newStyle
了AgentGameStyleFactory.cpp
std::unique_ptr<AgentGameStyle> newStyle
,这意味着将辅助方法用作AgentGameStyleFactory::instantiateHelper
是正确的做法吗?
您的编译器可以警告您有关return std::move(...)
-您可以(并且应该)简单地编写:
return newStyle;
我鼓励您放弃带有单独的new
的单独的帮助程序,而直接创建智能指针(假设使用C ++ 14或更高版本):
std::unique_ptr<AgentGameStyle> AgentGameStyleFactory::instantiate(const ePLAYING_CHARACTER pStyle)
{
switch(pStyle) {
case ePLAYING_CHARACTER::ePC_CONTAIN:
return std::make_unique<ContainGameStyleAgent>();
case ePLAYING_CHARACTER::ePC_COUNTER:
return std::make_unique<CounterGameStyleAgent>();
case ePLAYING_CHARACTER::ePC_STANDARD:
return std::make_unique<StandardGameStyleAgent>();
case ePLAYING_CHARACTER::ePC_ATTACKING:
return std::make_unique<AttackGameStyleAgent>();
case ePLAYING_CHARACTER::ePC_OVERLOAD:
return std::make_unique<OverloadGameStyleAgent>();
default:
return std::make_unique<StandardGameStyleAgent>();
}
}
不需要“ helper方法”返回原始指针,也不需要手动调用new
:
std::unique_ptr<AgentGameStyle>
AgentGameStyleFactory::instantiate(const ePLAYING_CHARACTER pStyle)
{
switch(pStyle)
{
case ePLAYING_CHARACTER::ePC_CONTAIN:
{
return std::make_unique<ContainGameStyleAgent>();
}
//...
default:
{
return std::make_unique<StandardGameStyleAgent>();
}
}
}
声明:本站的技术帖子网页,遵循CC BY-SA 4.0协议,如果您需要转载,请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.