C++ assignment operator during declaration

Question

This is my class Hero with two overload assignment operators - Hero to Hero and String to Hero.

#include <iostream> class Hero { private: int x; std::string name; public: Hero():x(42), name("JohnDoe") {}; Hero(int a, std::string b):x(a), name(b) {}; void print(){ std::cout<<name<<" : "<<x<<"\n"; } const Hero &operator =(const Hero &other){ std::cout<<"Overloaded Assignment class to class! \n"; x = other.x; name = other.name; return *this; } const Hero &operator =(const std::string N){ std::cout<<"Overloaded Assignment from string! \n"; x = 777; name = N; return *this; } }; int main(){ Hero foo(42, "Hercules"); Hero zak = foo; // Regular assignmnet, not the overloaded // Hero bar = "HelloWorld"; <<<< Illegal Hero zoo(HelloWorld",42); << Ok, but here we use constructor, not an assignment operator Hero bar; bar = "Ayax"; // "Overloaded Assignment from string! \n"; zak = bar; //"Overloaded Assignment class to class! \n"; zak.print(); bar.print(); }

And the produced result:

Overloaded Assignment from string! Overloaded Assignment class to class! Ayax : 777 Ayax : 777

Why can't I use overloaded operators for variable initialization in declaration?

In the line Hero zak = foo; compiler uses non-overloaded operator and the string Hero bar = "HelloWorld" is just illegal.

Initialization always invokes constructor and never assignment operator, presence of = is misleading. — user7860670
– user7860670, Commented Nov 5, 2020 at 8:54

Some programmer dude · Accepted Answer · 2020-11-05 08:54:30Z

When initializing an object at definition, it's not using assignment even when the = syntax is used.

When you do:

Hero zak = foo;

it's equivalent to:

Hero zak(foo);

Which is copy-initialization and as such invokes the copy-constructor.

The problem with

Hero bar = "HelloWorld";

is that it's equivalent to:

Hero bar = Hero("HelloWorld");

which in turn is equivalent to:

Hero bar(Hero("HelloWorld"));

And since you don't have a constructor for Hero("HelloWorld") it's invalid.

Collectives™ on Stack Overflow

C++ assignment operator during declaration

1 Answer 1

Comments

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Linked

Related