Cpp_part5

1.operator 重载运算符

class Account {
    int aid;
    char* name;
    int balance;

    
   public:
    Account(int id, int ab);
    void SaveMoney(int money);
    Account& operator+(int money);
    Account& operator++();
    Account operator++(int);
};
Account::Account(int id, int ab) {
    this->aid = id;
    this->balance = ab;
}
void Account::SaveMoney(int money) {
    this->balance += money;
}
Account& Account::operator+(int money) {
    this->balance += money;
    return *this;
}
Account Account::operator++(int) {
    Account a(*this);
    this->balance++;
    cout << "a++" << endl;
    return a;
}  //带占位符的为后加加
Account& Account::operator++() {
    this->balance++;
    cout << "++a" << endl;
    return *this;
}
void test01() {
    Account a(1001, 100);
    a.SaveMoney(100);
    a = a + 100;
    a++;
    ++a;
}

2.new vs malloc

分配空间方面无区别，行为有区别，new会调用构造函数，而malloc不会调用构造

new = malloc + construction

delete = destruct + free [注意顺序问题]

class Test {
    int* p;

   public:
    Test();
};
Test::Test() {
    cout << "construction" << endl;
    cout << sizeof(Test) << endl;  // 只有构造函数时，sizeof(Test)为1
}
void test02() {
    // new vs. malloc
    Test t;
    Test* p = (Test*)malloc(sizeof(Test));
    Test* q = new Test();
}

Main part

#include <bits/stdc++.h>
using namespace std;
int main() {
    test01();  // Operator
    test02();  // new delete
    return 0;
}