我目前正在使用 Visual Studio 2017 学习 C++，来自 C#/Java 背景。
我有一个关于在堆上创建对象并在以后正确引用它们的问题。到目前为止，我遇到了多个教程和做事方式。有些人建议尽可能多地使用智能指针，有些人则发誓它是魔鬼工具。
我目前的主要看起来像这样：
//Main
Person *makePerson()
{
string name;
int age;
cout << "Input name: ";
cin >> name;
cout << "Input age: ";
cin >> age;
return new Person(name, age);
}
Child *makeChild(Person &parent)
{
return new Child(*makePerson(), &parent);;
}
int main()
{
cout << "---Input parent data---" << endl;
Person *person = makePerson();
cout << "printing: " << *person << endl;
cout << "---Input child data---" << endl;
Child *child = makeChild(*person);
cout << "printing: " << *child << endl;
cout << "---end of main---" << endl;
delete person;
delete child;
return 0;
}
一个函数处理个人数据的输入并返回一个指向新 Person 对象的指针。然后我有一个函数通过获取父引用并询问 makePerson 剩余数据来处理子对象的创建。
这可以被认为是好的 C++ 吗？我怎样才能让它变得更好？我真的很感激一些代码示例。
正如一些人已经建议的那样，我可以用shared_ptr<Person> person（重）或unique_ptr<Person>（比共享更好）替换原始指针。
这是 Person 和子类的代码。请注意， Child 有一个类型为 的原始指针Person *parent。
//header
class Person
{
protected:
std::string name;
int age;
public:
Person();
Person(const Person& other);
Person(std::string inName, int inAge);
~Person();
virtual void print() const;
std::string getName() const;
int getAge() const;
Person &operator=(const Person &other);
//overload print functionality, act as if it was toString
friend std::ostream &operator<<(std::ostream &out, const Person &p);
};
//cpp
Person::Person() : name(""), age(0) {
std::cout << "Person empty constructor" << std::endl;
}
Person::Person(std::string inName, int inAge) : name(inName), age(inAge) {
std::cout << "Person (" << name << ") default constructor" << std::endl;
}
Person::Person(const Person & other) : name(other.name), age(other.age) {
std::cout << "Person (" << name << ") copy constructor" << std::endl;
}
Person::~Person() {
std::cout << "Person (" << name << ") destructor" << std::endl;
}
void Person::print() const {
std::cout << name << ", " << age << std::endl;
}
std::string Person::getName() const
{
return name;
}
int Person::getAge() const
{
return age;
}
Person & Person::operator=(const Person & other) {
std::cout << "Person (" << other.name << ") assignment constructor" << std::endl;
name = other.name;
age = other.age;
return *this;
}
std::ostream &operator<<(std::ostream &out, const Person &p) {
return out << p.name << ", " << p.age;
}
孩子是一个人，孩子知道孩子的父母是谁是有意义的。但是，我不确定如何处理这些“知识”。这是我用于子类的代码：
//Header
class Child : public Person
{
private:
const Person *parent;
public:
Child();
Child(std::string name, int age);
Child(std::string name, int age, const Person *parent);
Child(const Child &child, const Person *parent);
Child(const Person &person);
~Child();
Child &operator=(const Child &other);
void print() const;
friend std::ostream &operator<<(std::ostream &out, const Child &c);
};
//cpp
Child::Child() {
std::cout << "Child empty constructor" << std::endl;
}
Child::Child(std::string name, int age) : Person(name, age), parent(nullptr) {
std::cout << "Orphan (" << name << ") constructor" << std::endl;
}
Child::Child(std::string name, int age, const Person *parent) :
Person(name, age), parent(parent) {
std::cout << "Child (" << name << ") default constructor" << std::endl;
}
Child::Child(const Child &child, const Person *parent) :
Person(child.name, child.age), parent(parent) {
std::cout << "Child (" << child.name << ") copy constructor" << std::endl;
}
Child::Child(const Person &person) : Person(person), parent(nullptr) {
std::cout << "Child from person (" << name << ") constructor" << std::endl;
}
Child::~Child() {
std::cout << "Child (" << name << ") destructor" << std::endl;
}
Child & Child::operator=(const Child & other) {
name = other.name;
age = other.age;
parent = other.parent;
std::cout << "Child (" << name << ") assignment constructor" << std::endl;
return *this;
}
void Child::print() const {
if(parent)
std::cout << *this << " is child of " << *parent << std::endl;
else
std::cout << *this << " is orphan" << std::endl;
}
std::ostream &operator<<(std::ostream &out, const Child &c) {
return out << c.name << ", " << c.age << " is " <<
(c.parent ? ("child of " + c.parent->getName() + ", " + std::to_string(c.parent->getAge())) : "orphan");
}
这是我得到的输出：
我想我的问题仍然存在，谁能给我一个例子，说明它应该如何被认为是好的 C++？
@user4581301 如果您查看更新后的 main，您的意思是我应该返回 astd::unique_ptr而不是 a* (raw pointer)吗？在这种情况下，我的函数将如下所示：
std::unique_ptr<Person> makePerson2()
{
string name;
int age;
cout << "Input name: ";
cin >> name;
cout << "Input age: ";
cin >> age;
return std::unique_ptr<Person>(new Person(name, age));
}
变量声明为：
std::unique_ptr<Person> upParent = makePerson2();
cout << "printing: " << *upParent << endl;
这会被认为比我迄今为止所拥有的“更好”的 C++ 吗？