C++语法详解之封装、构造函数、析构函数

class Person {
 int age;
 
public:
 void setAge(int age){
  this->age = age;
 }
 
 int getAge(){
  return this->age;
 }
 
};

int main(){
 Person person;
 person.setAge(10);
 cout << person.getAge() << endl;
}

int *p = (int *)malloc(sizeof(int));
 *p = 10;
 free(p);
 
 int *p2 = new int;
 *p2 = 20;
 delete p2;
 
 int *p3 = new int[3];
 *p = 10;
 *(p+1) = 20;
 *(p+2) = 30;
 delete [] (p3);

 Person person;
 person.age = 10;
 person.height = 199;
 //从person的地址开始,每个字节都赋值为0
memset(&person, 0, sizeof(person));

int *p1 = (int *)malloc(sizeof(int)); //*p1 未初始化
int *p2 = (int *)malloc(sizeof(int));
memset(p2, 0, sizeof(int));//将 *p2 的每一个字节都初始化为0

int *p1 = new int;   //未初始化
int *p2 = new int();   //被初始化为0
int *p3 = new int(5);  //被初始化为5
int *p4 = new int[3];  //数组元素未被初始化
int *p5 = new int[3]();  //3个数组元素都被初始化0
int *p6 = new int[3]{};  //3个数组元素都被初始化0
int *p7 = new int[3]{5};  //数组首元素被初始化为5,其他元素被初始化为0

class Person{
public:
 int age;
 
 Person(){
  cout << "Person()" << endl;
 }
 
 Person(int age){
   cout << "Person(int age))" << endl;
 }
};

// 全局区
Person p1;  //调用Person()
Person p2(); //这是一个函数，函数名是p2,返回值类型是Person，无参
Person p3(18); //调用 Person(int)

int main(){
 //栈空间
 Person p4;  //调用Person()
 Person p5(); //这是一个函数，函数名是p5,返回值类型是Person，无参
 Person p6(18); //调用 Person(int)
 
 
 //堆空间
 Person *p7 = new Person;  //调用Person()
 Person *p8 = new Person(); //调用Person()
 Person *p9 = new Person(20); //调用 Person(int)
}

class Cat{
public:
 int age;
 Cat(){
  cout << "Cat()" << endl;
 }
 
 ~Cat(){
  cout << "~Cat()" << endl;
 }
};


class Person{
public:
 int age;
 Cat *cat;
 Person(){
  this->cat = new Cat();
  cout << "Person()" << endl;
 }
 
 ~Person(){
  cout << "~Person()" << endl;
 }
};

int main(){
 {
  Person person;
 }
 return 0;
}

~Person(){
  delete cat;
  cout << "~Person()" << endl;
 }