how to overload unique_ptr in a class . i am getting compilation error

Question

std::unique_ptr<Manager>& checkManager(std::unique_ptr<Manager> &p1) 
 {
   if(p1 && p1->getName().find("Manager") != std::string::npos ){
      std::cout<<"Manager exists"<<endl;
   }
   return p1;
 }

//overloading by unique ptr
 std::unique_ptr<Manager> checkManager(std::unique_ptr<Manager> p1) //by value passing uniq ptr
 {
   if(p1 && p1->getName().find("Manager")!=std::string::npos) {
      std::cout<<"Manager exists"<<endl;
   }
   return std::move(p1);
 }

i have overloaded these methods . in main when i am calling both i am getting error that function argument does not match . how to call these two methods separately from main.

Below is how i am calling these methods

 auto& resultRef = checkManager(mp1);  // it gives compilation error
 auto result = checkManager(std::move(mp1)); // it works

Below is the error: more than one instance of overloaded function "checkManager" matches the argument list:

Answer 1

You want the first overload to be called for lvalues and the second for rvalues.

You can do just that by making the second overload take an rvalue reference:

std::unique_ptr<Manager>& checkManager(std::unique_ptr<Manager> &p1) {
    // ...
    return p1;
}

std::unique_ptr<Manager> checkManager(std::unique_ptr<Manager> &&p1) {
    // ...
    return std::move(p1);
}

Before, when called with an lvalue, even though unique_ptr isn't copyable, it is still just a good a match (T& doesn't beat T when passed a T lvalue).

Now, the second overload cannot be called with an lvalue, so it is no longer ambiguous.