我有一个类 SourceComponent
及其派生类 PeriodicSourceComponent
。
实现是:
class SourceComponent : public Component
{
protected:
friend class UserInterface;
friend void readInput();
public:
virtual int returnType();
virtual int propagateLogic();
virtual void sourcePropagation(float);
virtual void accept(VisitorSources&);
SourceComponent();
};
和
#include "source_component.h"
class PeriodicSourceComponent : public SourceComponent
{
private:
int frequency;
friend void main();
friend void readInput();
friend class UserInterface;
public:
void sourcePropagation(float);
int returnType();
PeriodicSourceComponent();
};
当我尝试使用一些不同的类/方法时:
SourceComponent* s = new PeriodicSourceComponent;
它不会让我说“不能将 periodicblabla 类型的值分配给 sourceblabla 类型的值”。为什么?
编辑:
好的,在我看来,它看起来像这样:
#include "source_component.h"
#include "periodic_source_component.h"
void main()
{
SourceComponent* s = new PeriodicSourceComponent;
}
以及两个类的实现:
源代码.cpp:
#include "source_component.h"
SourceComponent::SourceComponent()
{
outputState = -1;
}
int SourceComponent::propagateLogic()
{
return 1;
}
int SourceComponent::returnType()
{
return 5;
}
和periodic.cpp
#include "periodic_source_component.h"
PeriodicSourceComponent::PeriodicSourceComponent()
{
outputState = 0;
}
int PeriodicSourceComponent::returnType()
{
return 3;
}
void PeriodicSourceComponent::sourcePropagation(float time)
{
float t = time, period;
period = 1000000/frequency;
if(t > period)
{
while(t >= period)
t -= period;
}
if(t <= (period/2))
outputState = 0;
else
outputState = 1;
}
它不起作用...(outputState 是 Component 类的成员,SourceComponent 的基类)
和错误消息:无法将“PeriodicSourceComponent*”类型的值分配给“SourceComponent*”类型的值。
重要编辑 当我尝试编译时,实际的编译器错误是在 PeriodicSourceComponent 声明处,它说:“基类未定义”。
此外,我还有两个来自 SourceComponent 的派生类,但我看不出它们如何干扰这个......
编辑 4 好的,所以我弄清楚了导致错误的原因,您当然是对的,这是我没有发布的其他内容。我有 VisitorSources 类,继承人定义:
#ifndef __VISITOR_SOURCES_H__
#define __VISITOR_SOURCES_H__
#include "component.h"
#include "impulse_source_component.h"
#include "arbitrary_source_component.h"
#include "periodic_source_component.h"
class VisitorSources
{
protected:
VisitorSources();
public:
virtual void visitImpulseSource(ImpulseSourceComponent*);
virtual void visitArbitrarySource(ArbitrarySourceComponent*);
virtual void visitPeriodicSource(PeriodicSourceComponent*);
void visitSource(int, float);
};
#endif
它的实现还没有写:
#include "visitor_sources.h"
void visitSource(int type, float time)
{
}
void VisitorSources::visitArbitrarySource(ArbitrarySourceComponent* a)
{
}
当我注释掉整个Visitor类和实现时,不知为何上述错误都没有了。我不知道为什么...
剩下的唯一错误是,当我尝试使用 s->frequency 时,它说频率不是 SourceComponent 的成员,这是真的,但它是 PeriodicSourceComponent 的成员,这就是我使用强制转换的原因首先..
最后,这是组件类,项目中几乎所有其他类的主类:P
#ifndef __COMPONENT_H__
#define __COMPONENT_H__
#include <iostream>
#include <vector>
class Component
{
friend class UserInterface;
friend void readAndSimulate();
protected:
Component();
int numOfInputs;
int numOfOutputs;
std::vector<Component*> inputs;
std::vector<Component*> outputs;
friend void main();
float lengthOfSimulation;
int typeIfSource;
public:
int outputState;
virtual int propagateLogic() = 0;
virtual int returnType();
int beginPropagation();
virtual void sourcePropagation(float);
~Component();
};
#endif
和实现:
#include "component.h"
#include <conio.h>
Component::Component()
{
}
int Component::beginPropagation()
{
std::vector<Component*>::const_iterator iter = outputs.begin();
for(;iter<outputs.end();++iter)
{
if ((*iter)->outputState == -2)
{
(*iter)->outputState = outputState;
return (*iter)->outputState;
}
}
std::vector<Component*>::const_iterator it = outputs.begin();
int finishedCycle, x;
while(1)
{
finishedCycle = 1;
for(; it < outputs.end(); ++it)
{
x = (*it)->propagateLogic();
if(!x)
finishedCycle = 0;
}
if(finishedCycle) break;
it = outputs.begin();
}
it = outputs.begin();
for(;it<outputs.end();++it)
(*it)->beginPropagation();
}
int Component::returnType()
{
return 0;
}
void Component::sourcePropagation(float)
{
}
Component::~Component()
{
std::vector<Component*>::const_iterator it = inputs.begin();
for(; it < inputs.end(); ++it)
{
if((*it) != NULL)
{
delete *it;
Component* p = *it;
p = NULL;
}
}
it = outputs.begin();
for(; it < inputs.end(); ++it)
{
if((*it) != NULL)
{
delete *it;
Component* p = *it;
p = NULL;
}
}
}
最佳答案
你在使用 include guards在所有头文件中?
没有它们会导致您遇到的各种问题。
关于c++ - 简单多态转换不起作用,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/9173975/