如何解决这个构建错误：在UNIX下的C ++中“没有匹配的函数调用”？

Question

How can I solve this build error: "no matching function for call to" in C++ under UNIX?

I am getting the following build error:

unixserver:Lab1> make
g++ -o LSL lab1.cpp Employee.cpp
lab1.cpp: In function int main():
lab1.cpp:199: error: no matching function for call to LinkedSortedList<Employee>::find(std::string&)
LinkedSortedList.cpp:137: note: candidates are: bool LinkedSortedList<Elem>::find(Elem) const [with Elem = Employee]
make: *** [main] Error 1

Here is my find function:

// Check to see if "value" is in the list.  If it is found in the list,
// return true, otherwise return false.  Like print(), this function is
// declared with the "const" keyword, and so cannot change the contents
// of the list.
template<class Elem>
bool LinkedSortedList<Elem>::find(Elem searchvalue) const {
         if (head == NULL) {
                 return false;
         } else {
                 while (head != NULL) {
                    LinkedNode<Elem>* pointer;
                    for (pointer = head; pointer != NULL; pointer = pointer->next) 
                        if (pointer->value == searchvalue) {
                            return true;
                        }
                  }
         }
         return false;
 }

And this is in my LinkedSortedList.h file under the "public:" section:

bool find(Elem searchvalue) const;

Here is the missing code: line 199

                        case 'S':
                                cout << "Save database to a file selected\n\n";
                                // TODO call function to save database to file
                                // File I/O Save to file
                                cout << "Please enter a file name: " << endl;
                                cin >> fileName;
                                {char* file = (char*) fileName.c_str();
                                writeFile(file, database);}
                                break;

Answer 1

Your problem is, as the error message states, that you are trying to invoke this function:

LinkedSortedList::find(std::string&)

but it doesn't exist.

You have three options:

1. Create that function. In the public section of LinkedSortedList declare (and subsequently implement) something like find(const std::string&) ;

2. Don't invoke that function. In your test program, call list.find(elem) instead of list.find(str) , for example.

3. Make Employee implicitly constructable from std::string . Add a new public constructor to Employee that takes a single std::string as a parameter.