Comments (3)
line4 class Visitor;
这里的前置声明无法编译,因为
line19 visitor.visitElementA(*this);
这里用到了类成员。仅当我们使用类引用或者指针时前置声明才有用,这样是编译不过去的。
应该把类Visitor定义提前,放在line4处
#include <iostream> using namespace std; class Visitor{ public: virtual void visitElementA(ElementA& element) = 0; virtual void visitElementB(ElementB& element) = 0; virtual ~Visitor(){} }; class Element { public: virtual void accept(Visitor& visitor) = 0; //第一次多态辨析 virtual ~Element(){} }; ...
#include "Visitor.h"不好吗?
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@dxgzg 好啊,但作者没这么写。这个问题到现在还没fix..
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这样改,还是要前置声明ElementA 和 ElementB
`
#include
using namespace std;
class ElementA;
class ElementB;
class Visitor{
public:
virtual void visitElementA(ElementA& element) = 0;
virtual void visitElementB(ElementB& element) = 0;
virtual ~Visitor(){}
};
class Element
{
public:
virtual void accept(Visitor& visitor) = 0; //第一次多态辨析
virtual ~Element(){}
};
...
`
from cpp-design-patterns.
Related Issues (2)
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