C++ Primer
cpp primer
move constructors
pass by reference is passing in an object from the caller to the callee as a function argument to do as the callee wishes, effectively temporarily handing control (without moving the memory location)
returning a reference is handing control of the callee's own variable to the caller without moving the memory location
#include <iostream>
#include <string>
class Person {
public:
Person(std::string name, int age) : name_(std::move(name)), age_(age) {}
// Function that takes a reference parameter
void incrementAge(int& yearsToAdd) {
age_ += yearsToAdd;
yearsToAdd = 0; // This change will be visible to the caller
}
// Function that returns a reference
std::string& getName() {
return name_; // Returns a reference to name_
}
void printDetails() const {
std::cout << "Name: " << name_ << ", Age: " << age_ << std::endl;
}
private:
std::string name_;
int age_;
};
int main() {
Person person("Alice", 30);
// Demonstrating pass by reference
int years = 5;
std::cout << "Before incrementAge: years = " << years << std::endl;
person.incrementAge(years);
std::cout << "After incrementAge: years = " << years << std::endl;
person.printDetails();
// Demonstrating returning a reference
std::cout << "\nBefore modifying name: ";
person.printDetails();
person.getName() = "Alicia"; // Directly modifies the name_ member
std::cout << "After modifying name: ";
person.printDetails();
return 0;
}
Reference v Pointer
a reference has the same memory address as the object it references; it is an alias.
a pointer has a different memory address and its value is the memory address of another object of the same type
#include <iostream>
#include <string>
class Person {
public:
Person(std::string name, int age) : name_(std::move(name)), age_(age) {}
Person& returnReference() {
std::cout << "Returning *this (reference)\n";
return *this;
}
Person* returnPointer() {
std::cout << "Returning this (pointer)\n";
return this;
}
void printDetails() const {
std::cout << "Name: " << name_ << ", Age: " << age_ << std::endl;
}
private:
std::string name_;
int age_;
};
int main() {
Person alice("Alice", 30);
std::cout << "Original Alice:\n";
alice.printDetails();
std::cout << "\nUsing returnReference():\n";
Person& aliceRef = alice.returnReference();
std::cout << "Address of alice: " << &alice << std::endl;
std::cout << "Address of aliceRef: " << &aliceRef << std::endl;
std::cout << "\nUsing returnPointer():\n";
Person* alicePtr = alice.returnPointer();
std::cout << "Address of alice: " << &alice << std::endl;
std::cout << "Value of alicePtr (address it points to): " << alicePtr << std::endl;
std::cout << "Address of alicePtr itself: " << &alicePtr << std::endl;
return 0;
}
