c-如何将子类的向量传递到需要父类向量的函数中？

我可以将Child传递给需要Parent的成员函数,但是当使用向量时,出现编译错误,指出没有匹配的声明.请参阅底部对getUniqueLabels()的CorrelationEngineManager.cpp调用

ServerEvent.h

#ifndef SERVEREVENT_H
#define SERVEREVENT_H

#define SERVEREVENT_COLS 3

#include "Event.h"
#include <vector>


class ServerEvent: public Event {
private:

public: 
    ServerEvent(std::vector<std::string> tokens);
    void print();
};

#endif

Event.h

#ifndef EVENT_H
#define EVENT_H

#include <string>

#define EVENT_STOP 0
#define EVENT_START 1

class Event {
private:

protected:
    double time;
    std::string label;
    int type; // EVENT_START OR EVENT_STOP

public:

};

#endif

CorrelationEngineManager.h

class CorrelationEngineManager {
private:
    std::vector<ServerEvent> s_events;
    std::vector<UPSEvent> u_events;
    std::vector<TimeRecord> s_timeRecords;
    std::vector<TimeRecord> u_timeRecords;
    // typeOfEvent gets type of event, 0 for error, look at #defines for codes
    int typeOfEvent(std::vector<std::string>);
    int createTimeRecords();
    std::vector<std::string> getUniqueLabels(std::vector<Event> events);


public:
    CorrelationEngineManager();
    //~CorrelationEngineManager();
    int addEvent(std::vector<std::string> tokens); //add event given tokens
    void print_events();
};

CorrelationEngineManager.cpp

int CorrelationEngineManager::createTimeRecords() {
    std::vector<std::string> u_sLabels; // unique server labels
    std::vector<std::string> u_uLabels; // unique UPS labels
    u_sLabels = getUniqueLabels(s_events);
//  u_uLabels = getUniqueLabels(u_events);
    return 1;
}
// returns a vector of unique labels, input a vector of events
std::vector<std::string> CorrelationEngineManager::getUniqueLabels(std::vector<Event> events) {

    std::vector<std::string> temp;
    return temp;
}

编译错误

 CorrelationEngineManager.cpp: In member function ‘int CorrelationEngineManager::createTimeRecords()’:
 CorrelationEngineManager.cpp:60: error: no matching function for call
 to ‘CorrelationEngineManager::getUniqueLabels(std::vector<ServerEvent,
 std::allocator<ServerEvent> >&)’ CorrelationEngineManager.h:23: note:
 candidates are: std::vector<std::basic_string<char,
 std::char_traits<char>, std::allocator<char> >,
 std::allocator<std::basic_string<char, std::char_traits<char>,
 std::allocator<char> > > >
 CorrelationEngineManager::getUniqueLabels(std::vector<Event,
 std::allocator<Event> >) make: *** [CorrelationEngineManager.o] Error 1

解决方法:

在C中这是不可能的,这需要称为协方差的功能.

即使类型A是类型B的子类,类型X A仍然是类型A.完全与X B类型无关.

因此,您不能通过std :: vector< UPSEvent>因为它们是不相关的类型,所以将其传递给期望std :: vector< Event>的函数.即使通过引用/指针传递也不起作用.

有两种方法可以解决此问题.

一种是使两个向量都持有指向Event的指针,然后它们将具有相同的类型.

另一个方法是,按照Daniel的建议,使函数成为模板函数.

正如Billz指出的那样,您还需要修复签名.

标签：c,vector,parent-child
来源： https://codeday.me/bug/20191011/1894058.html