c++ - Custom operators error when passing parameters c++

Question

I'm building custom operators and im having problems when passing parameters to them.

For example

class test{
     public:
        test operator[](vector <string> s){
            test a;
            return a;
         }
}; 

Now if I wanted in my main program to do something like this

 int main(){

    test d;
    vector<string> s;
    s.push_back("bla");
    d[s];
 }

I get a bunch of errors. Is it because I need to have const somewhere or I don't know.

Also I have built in a custom operator for printing out the class test ( << operator ). Now I don't get compile error when calling d[s] in main program but I get compile error when calling cout<< d[s] in main program. The operator << is working because I tested it with simple cout<< d

Answer 1

return test;

test是一种类型。你不能返回一个类型。也许你的意思是：

return a;

但是，您还有另一个问题，因为您要返回对局部变量的引用。当函数返回时，对象a将被销毁（因为这是它的作用域），因此引用将悬空。

Answer 2

Code working fine using gcc compiler.

#include <string>
#include <vector>
using namespace std;

class test{
     public:
        test operator[](vector <string> s){
            test a;
            return a;
         }
};

int main(){

    test d;
    vector<string> s;
    s.push_back("bla");
    d[s];
 }

Answer 3

尽管其他人已经指出了错误（悬空引用，返回类型而不是值），但请注意，如果您打算覆盖 []，您还应该考虑覆盖指针引用运算符（一元 *）。交替使用它们。