[C++知识库]c++静态对象、动态对象以及友元函数

1. 静态对象

#include<iostream>
#include<string>
using namespace std;
#if 0
class student {
private:
	int id;
	string name;
	int age;
	string sex;
public:
	void set(int id,string name,int age,string sex) {
		this->id = id;
		this->name = name;
		this->age = age;
		this->sex = sex;
	}
	/*
	student(int id, string name, int age,string sex) {
		this->id = id;
		this->name = name;
		this->age = age;
		this->sex = sex;
	}*/
	void get() {
		cout << id <<" "<< name<<" " << age <<" "<< sex << endl;
	}
	/*
	student(student &a)//其形参是本类的对象的引用。
	{
		id = a.id;
		name = a.name;
		age = a.age;
		sex = a.sex;
	}*/
};

int main() {
	student st;
	st.set(1, "李三", 23, "f");
	st.get();
	//student s1(2, "李三", 23, "f");
	//s1.get();
	//student s2(3, "李五", 44, "f");
	//s2.get();
}
#endif

2. 动态对象数组

#include<iostream>
#include<string>
using namespace std;
#if 0
class animal {
private:
	int id;
	string name;
	int age;
public:
	void eat() {
		cout <<name<< "吃草"<<endl;
	}
	void drink() {
		cout <<name<< "喝水"<<endl;
	}
	
	animal() {
		cin >> id;
		cin >> name;
		cin >> age;

	}

	animal(int id,string name,int age) {
		this->id = id;
		this->name = name;
		this->age = age;

	}
	void show() {
		cout << id << name << age<<endl;
	}
};

int main() {
	animal a;
	animal a1[3]{ {1,"cat",5},{2,"dog",7}, {3,"tiger",10} };
	animal a2(4, "pandas", 6);
	a1[0].eat();
	a1[1].eat();
	a1[2].eat();
	a2.eat();
	a.drink();
	cout << "-------------------" << endl;
	animal *p = new animal(4, "pandas", 6);
	animal *p1 = new animal[3] {{1,"cat",5},{2,"dog",7}, {3,"tiger",10}};
	p->show();
	p1[0].show();
	p1[1].show();
	p1[2].show();
	p1->show();
	(p1 + 1)->show();
	(p1 + 2)->show();
	delete p;
	delete[]p1;
}
#endif

3. 友元函数

#include<iostream>
#include<string>
using namespace std;
#if 0
//友元函数
class student {
private:
	int id;
	string name;
	int age;
public:
	student(int id, string name, int age) {
		this->id = id;
		this->name = name;
		this->age = age;

	}
	friend void show(student &s);

};
void show(student &s) {
	cout << s.id << s.name << s.age<<endl;
}
int main() {
	student s(1,"张三",18);
	show(s);
	student s1[2]{{2,"李四",24},{3,"王五",22}};
	show(s1[0]);
	show(s1[1]);
}
#endif //1