嵌入式linux基础：c++（五）构造函数

2022-12-14 160

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简介： 嵌入式linux基础：c++（五）构造函数

1. 构造函数

为什么引入构造函数？

看一看之前写的程序：

如图所示，该部分的设置名字以及设置年龄分别用来两个函数，这回变的非常麻烦。所以提出构造函数的概念，

#include <iostream>
using namespace std;
class Person {
private:
  char *name;
  int age;
  char *work;
public:
  Person() {cout <<"Pserson()"<<endl;}
  Person(char *name) 
  {
  cout <<"Pserson(char *)"<<endl;
  this->name = name;
  }
  Person(char *name, int age, char *work = "none") //char *work = "none",初始化的时候如果说，work没有参数，那么就赋值none
  {
  cout <<"Pserson(char*, int)"<<endl;
  this->name = name;
  this->age = age;
  this->work = work;
  }
//构造函数，没有返回值，没有定义返回类型。
/*  void setName(char *n)
  {
  name = n;
  }
  int setAge(int a)
  {
  if (a < 0 || a > 150)
  {
    age = 0;
    return -1;
  }
  age = a;
  return 0;
  }
*/
  void printInfo(void)
  {
  //printf("name = %s, age = %d, work = %s\n", name, age, work); 
  cout<<"name = "<<name<<", age = "<<age<<", work = "<<work<<endl;
  }
};
int main(int argc, char **argv)
{
  Person per("zhangsan", 16);//根据函数参数调用函数
  Person per2;   /* 调用无参数构造函数 */
  Person per3(); /* int fun(); */
  per.printInfo();
  return 0;
}

我们还有没有其他办法来实例化一个对象呢？

有的，这里我们直接定义

#include <iostream>
using namespace std;
class Person {
private:
  char *name;
  int age;
  char *work;
public:
  Person() {cout <<"Pserson()"<<endl;}
  Person(char *name) 
  {
  cout <<"Pserson(char *)"<<endl;
  this->name = name;
  }
  Person(char *name, int age, char *work = "none") 
  {
  cout <<"Pserson(char*, int)"<<endl;
  this->name = name;
  this->age = age;
  this->work = work;
  }
/*  void setName(char *n)
  {
  name = n;
  }
  int setAge(int a)
  {
  if (a < 0 || a > 150)
  {
    age = 0;
    return -1;
  }
  age = a;
  return 0;
  }
*/
  void printInfo(void)
  {
  //printf("name = %s, age = %d, work = %s\n", name, age, work); 
  cout<<"name = "<<name<<", age = "<<age<<", work = "<<work<<endl;
  }
};
int main(int argc, char **argv)
{
  Person per("zhangsan", 16);
  Person per2;   /* 调用无参数构造函数 */
  Person per3(); /* int fun(); */
  Person *per4 = new Person;//临时动态创建一个person
  Person *per5 = new Person();
  //我们使用关键字new在堆上动态创建一个对象时，它实际上做了三件事：获得一块内存空间、调用构造函数、返回正确的指针。
  Person *per6 = new Person[2];
  Person *per7 = new Person("lisi", 18, "student");
  Person *per8 = new Person("wangwu", 18);
  per.printInfo();
  per7->printInfo();
  per8->printInfo();
  delete per4;
  delete per5;
  delete []per6;
  delete per7;
  delete per8;
//删掉new创建出来的内存
  return 0;
}