c++ 传递引用给对象

[c++]代码库

#include <iostream>
using namespace std;

class SimpleCat {
public:
	SimpleCat();
	SimpleCat(SimpleCat&);
	~SimpleCat();

	int GetAge() const {
		return itsAge;
	}
	void SetAge(int age) {
		itsAge = age;
	}

private:
	int itsAge;
};

SimpleCat::SimpleCat() {
	cout << "Simple Cat Constructor..." << endl;
	itsAge = 1;
}

SimpleCat::SimpleCat(SimpleCat&) {
	cout << "Simple Cat Copy Constructor..." << endl;
}

SimpleCat::~SimpleCat() {
	cout << "Simple Cat Destructor..." << endl;
}

const SimpleCat & FunctionTwo(const SimpleCat & theCat);

int main() {
	cout << "Making a cat..." << endl;
	SimpleCat Frisky;
	cout << "Frisky is " << Frisky.GetAge() << " years old" << endl;
	int age = 5;
	Frisky.SetAge(age);
	cout << "Frisky is " << Frisky.GetAge() << " years old" << endl;
	cout << "Calling FunctionTwo..." << endl;
	FunctionTwo(Frisky);
	cout << "Frisky is " << Frisky.GetAge() << " years old" << endl;

	return 0;
}

// functionTwo, passes a ref to a const object
const SimpleCat & FunctionTwo(const SimpleCat & theCat) {
	cout << "Function Two. Returning..." << endl;
	cout << "Frisky is now " << theCat.GetAge();
	cout << " years old " << endl;
	// theCat.SetAge(8); const!
	return theCat;
}