Question

我正在使用ROOT frameowrk，我想写一个有TMultiGraph成员的类。我试图为我的班级编写和分配操作符但是由于compilaton问题我失败了。课程TMultiGraph将其作为protected的作业运算符保留。

我班级的标题：

#include "../include/clipper.hpp"
#include "TMultiGraph.h"
#include "TColor.h"
#include "RtypesCore.h"

using namespace ClipperLib;

class ClipperDraw : protected TMultiGraph {

public:
    ClipperDraw() {}

    ClipperDraw& operator=(const ClipperDraw &c);

private:
    TMultiGraph mg;

};

.cpp是：

ClipperDraw& ClipperDraw::operator=(const ClipperDraw &c)
{
    mg = c.mg;
    return *this;
}

编译时我收到此消息：

g++ -fPIC -Wall `root-config --cflags` -I./include -O2  -c -o obj/ClipperDraw.o src/ClipperDraw.cpp
In file included from src/../include/ClipperDraw.h:12:0,
                 from src/ClipperDraw.cpp:8:
/home/user/anaconda3/envs/deepjetLinux3/include/TMultiGraph.h: In member function ‘ClipperDraw& ClipperDraw::operator=(const ClipperDraw&)’:
/home/user/anaconda3/envs/deepjetLinux3/include/TMultiGraph.h:47:17: error: ‘TMultiGraph& TMultiGraph::operator=(const TMultiGraph&)’ is protected
    TMultiGraph& operator=(const TMultiGraph&);
                 ^
src/ClipperDraw.cpp:26:5: error: within this context
  mg = c.mg;
     ^
Makefile:19: recipe for target 'obj/ClipperDraw.o' failed
make: *** [obj/ClipperDraw.o] Error 1

Answer 1

TMultiGraph的复制构造函数和复制赋值运算符都标记为受保护。这意味着您无法将TMultiGraph分配给其他TMultiGraph。继承对你没有帮助，因为它不会改变这个事实。

从TMultiGraph继承的内容是允许创建自己可以复制的图表类。那看起来像是

class MyMultiGraph : public TMultiGraph {
    //...
public:
    MyMultiGraph& operator =(const MyMultiGraph& rhs)
    {
        TMultiGraph::operator=(rhs);
        // assign MyMultiGraph member here
    }
};

ROOT类的C ++赋值运算符

1 个答案: