C++ 面向对象

1. 面向对象小例子

#include <iostream>
using namespace std;
class bad_hmean {
private:
  double v1;
  double v2;

public:
  bad_hmean (int a=0, int b=0): v1(a), v2(b){};
  // 上下这么写是一样的意思 , 有时候看见上面的都不知道什么意思， 所以这里也就记录一下
  // bad_hmean (int a=0, int b=0){v1=a, v2=b}; 
  // virtual ~bad_hmean ();
  void mesg();
};

inline void bad_hmean::mesg(){
  std::cout << "hmean(" << v1 << ", " << v2 << "): " << "invalid arguments: a = -b
" << '
';
}

int main(int argc, char const *argv[]) {
  bad_hmean(1, 2).mesg();
  // bg.mesg();
  return 0;
}

下面是经常写的， 高级封装， 把类进行拆分， 类和方法分开的形式

// 目录和文件都小写， 重要的事情才大写

// 类的名字首字母大写
#include <iostream>
#include <string>

#include "Per.h"

Person::Person()
{
  std::cout << "构造函数： " << this->testAbc << '
';
}
Person::~Person()
{
  std::cout << "析构函数： " << this->testAbd << '
';
}


void Person::setpid(int pid)
{
    this->_pid = pid; // this 表示当前对象下的_pid
}
int Person::getpid()
{
  return this->_pid;
}

void Person::setname(string name)
{
  this->_name = name;
}
string Person::getname()
{
  return _name;
}

void Person::setage(int age)
{
  this->_age = age;
}
int Person::getage()
{
  return _age;
}

int main(){
  // 锦绣城， 双滦区 2区观鱼园
  // -----普通方式----- //
  /*
  Person per;
  per.setpid(1);
  per.setname("tom");
  per.setage(20);

  int pid = per.getpid();
  string name = per.getname();
  int age = per.getage();

  std::cout << "pid: " << pid << "  ";
  std::cout << "name: " << name<< "  ";
  std::cout << "age: " << age << '
';
  */

  // -----指针方式-----//
  Person *per = new Person();
  per->setpid(1);
  per->setname("Baker");
  per->setage(20);

  int pid = per->getpid();
  string name = per->getname();
  int age = per->getage();
  //  delete前打印的  //
  std::cout << "pid: " << pid << "  ";
  std::cout << "name: " << name<< "  ";
  std::cout << "age: " << age << '
';
  
  delete per;

  //  delete 后打印的  //
  std::cout << "pid: " << pid << "  ";
  std::cout << "name: " << name<< "  ";
  std::cout << "age: " << age << '
';

  return 0;
}

#include <iostream>
#include <string>
using namespace std;
class Person
{
    private:
        int _pid;
        string _name;
        int _age;

    public:
      int testAbc = 123;
      int testAbd = 124;

        Person();
        ~Person();

        void setpid(int pid);
        int getpid();

        void setname(string name);
        string getname();

        void setage(int age);
        int getage();
};