本文介绍了是否使用继承和多态性重载';<;<;';?的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!
问题描述
以下是代码外观的粗略示例,问题是如何让DerivedOne和DerivedTwo拥有重载的<;<;运算符,而将这些对象存储在Base*的向量中。
至于我要实现的目标;我希望能够遍历对象向量,并输出我在DerivedOne和DerivedTwo中告诉它的信息。
vector<Base*> objects;
class Base
{
private:
object Data
public:
object getData() { return Data; }
};
class DerivedOne : public Base
{
}
class DerivedTwo : public Base
{
}
现在我知道有这个,但它不会达到我的目的。
friend ostream &operator<<(ostream &stream, Object object)
{
return stream << "Test" << endl;
}
推荐答案
Make your virtual methods private to separate how an object is used from how its behavior can be customized by derived classes.
这里有一个类似于其他答案的解决方案,但虚拟方法是私有的:
#include <iostream>
namespace {
class Base {
// private (there is no need to call it in subclasses)
virtual std::ostream& doprint(std::ostream&) const = 0;
public:
friend std::ostream& operator << (std::ostream& os, const Base& b) {
return b.doprint(os); // polymorphic print via reference
}
virtual ~Base() {} // allow polymorphic delete
};
class DerivedOne : public Base {
std::ostream& doprint(std::ostream& os) const {
return os << "One";
}
public:
DerivedOne() { std::cerr << "hi " << *this << "
"; } // use << inside class
~DerivedOne() { std::cerr << "bye " << *this << "
"; }
};
}
示例
#include <memory>
#include <vector>
int main () {
using namespace std;
// wrap Base* with shared_ptr<> to put it in a vector
vector<shared_ptr<Base>> v{ make_shared<DerivedOne>() };
for (auto i: v) cout << *i << " ";
cout << endl;
}
输出
hi One
One
bye One
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