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[英]Transform vector of reference wrapper to Base class to vector of reference_wrapper to Derived class cannot dynamic cast
[英]Transform std:vector<reference_wrapper<Base>> to std:vector<reference_wrapper<Derived>> Runtime error time: 0 memory: 3412 signal:6
我正在嘗試將對基礎對象的引用向量轉換為對派生對象的引用向量。 一切都編譯良好,但我收到此錯誤:運行時錯誤時間:0內存:3412 signal:6
這是我的代碼:
#include <iostream>
#include <vector>
#include <algorithm>
#include <functional>
using namespace std;
struct B {
B(int i) { b = i; }
virtual ~B() {}
int b;
};
struct D: public B {
D(int i): B(i) {}
};
typedef vector<reference_wrapper<B>> refB;
typedef vector<reference_wrapper<D>> refD;
void dynamicCast(refB &b, refD &d)
{
for(const auto& bb: b)
{
d.push_back(dynamic_cast<D&> (bb.get()));
}
}
int main() {
vector<B*> numbers;
refB refNumbers;
refD dNumbers;
for(int i = 0; i < 10; i++)
{
numbers.push_back(new B(2*i));
refNumbers.push_back(*numbers[i]);
}
dynamicCast(refNumbers, dNumbers);
return 0;
}
dynamicCast()函數怎么了?
編輯:@John Zwinck答案有所幫助,但是當我嘗試在我的代碼中執行此操作時,出現編譯錯誤:
無法將'(&obj)-> std :: reference_wrapper <_Tp> :: get()'(類型為'MEPObject'類型)'動態轉換為'類MEPGene&'(目標不是指針或對完整類型的引用)基因。 (dynamic_cast(obj.get()));
class MEPObject;
class MEPGene;
typedef std::vector<std::reference_wrapper<MEPObject>> MEPObjects;
typedef std::vector<std::reference_wrapper<MEPGene>> MEPGenes;
void dynamicCast(MEPObjects &objects, MEPGenes &genes)
{
for(const auto &obj: objects)
{
genes.push_back(dynamic_cast<MEPGene&> (obj.get()));
}
}
^
dynamicCast()
。 問題在這里:
numbers.push_back(new B(2*i));
您只能構造作為基類的B
實例。 您不可能將它們D
為派生類D
也許您打算構造派生實例並將其存儲在對base的引用向量中。
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