• C++_默认值拷贝构造函数_构造函数顺序

    C++_默认值拷贝构造函数_构造函数顺序

    1、创建类时除了析构和构造函数还有一种值拷贝构造函数
    注意：值拷贝构造函数是用于整个类对象给另一个类对象赋值的比如这样（Person per2(per);）把实例化的per里面的参数值复制给per2，他们使用的是同一片内存空间，当per释放的时候，per2也不能使用了

    #include 
#include 
#include 

using namespace std;

class Person {
private:
	char *name;
	int age;
	char *work;

public:

	Person() {//cout <<"Pserson()"<
		name = NULL;
		work = NULL;
	}
	Person(char *name) 
	{
		//cout <<"Pserson(char *)"<
		this->name = new char[strlen(name) + 1];
		strcpy(this->name, name);
		this->work = NULL;
	}

	Person(char *name, int age, char *work = "none") 
	{
		//cout <<"Pserson(char*, int)"<
		this->age = age;

		this->name = new char[strlen(name) + 1];
		strcpy(this->name, name);

		this->work = new char[strlen(work) + 1];
		strcpy(this->work, work);
	}

	~Person()
	{
		cout << "~Person()"<<endl;
		if (this->name) {
			cout << "name = "<<name<<endl;
			delete this->name;
		}
		if (this->work) {
			cout << "work = "<<work<<endl;
			delete this->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", 18);
	Person per2(per);

	per2.printInfo();

	return 0;
}

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    2、实现自己的值拷贝函数
    注意：实现过程实际就是自己写一个（传入参数是对象）重载构造函数

    Person(Person &per) 
{
	cout <<"Pserson(Person &)"<<endl;
	this->age = per.age;

	this->name = new char[strlen(per.name) + 1];
	strcpy(this->name, per.name);

	this->work = new char[strlen(per.work) + 1];
	strcpy(this->work, per.work);
}

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    3、构造函数的顺序
    注意：
    ①按照运行中定义对象的顺序调用构造函数
    ②静态对象只调用一次构造函数
    ③全局对象在main函数执行前被调用
    ④局部对象在执行完会被析构函数销毁

    在这里插入图片描述

    #include 
#include 
#include 

using namespace std;

class Person {
private:
	char *name;
	int age;
	char *work;

public:

	Person() {//cout <<"Pserson()"<
		name = NULL;
		work = NULL;
	}
	Person(char *name) 
	{
		//cout <<"Pserson(char *)"<
		this->name = new char[strlen(name) + 1];
		strcpy(this->name, name);
		this->work = NULL;
	}

	Person(char *name, int age, char *work = "none") 
	{
		cout <<"Pserson(char*, int), name = "<<name<<", age= "<<age<<endl;
		this->age = age;

		this->name = new char[strlen(name) + 1];
		strcpy(this->name, name);

		this->work = new char[strlen(work) + 1];
		strcpy(this->work, work);
	}

	Person(Person &per) 
	{
		cout <<"Pserson(Person &)"<<endl;
		this->age = per.age;

		this->name = new char[strlen(per.name) + 1];
		strcpy(this->name, per.name);

		this->work = new char[strlen(per.work) + 1];
		strcpy(this->work, per.work);
	}

	~Person()
	{
		cout << "~Person()"<<endl;
		if (this->name) {
			cout << "name = "<<name<<endl;
			delete this->name;
		}
		if (this->work) {
			cout << "work = "<<work<<endl;
			delete this->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;
	}
};

Person per_g("per_g", 10);

void func()
{
	Person per_func("per_func", 11);  //函数执行完即使销毁了
	static Person per_func_s("per_func_s", 11);
}

int main(int argc, char **argv)
{
	Person per_main("per_main", 11);
	static Person per_main_s("per_main_s", 11);

	for (int i = 0; i < 2; i++)
	{
		func();
		Person per_for("per_for", i);
	}

	return 0;
}

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    类里面嵌套其他对象（类似结构体中包含其他结构体）
    注意：
    ①当自己已经定义了一个带有参数的构造函数，那么系统将不再给你分配默认的无参数的构造函数，必须自己加上一个无参的构造函数
    ②析构函数的调用顺序和构造函数相反的
    ③下面例子可以完成在初始化学生类时候，一起把他包含的父母类也一起初始化了
    ④当学生类里面包含其他类的时候，学生类实例化的时候，构造函数的顺序是先父亲再母亲最后自己

    #include 
#include 
#include 

using namespace std;

class Person {
private:
	char *name;
	int age;
	char *work;

public:

	Person() {
		cout <<"Pserson()"<<endl;
		name = NULL;
		work = NULL;
	}
	Person(char *name) 
	{
		//cout <<"Pserson(char *)"<
		this->name = new char[strlen(name) + 1];
		strcpy(this->name, name);
		this->work = NULL;
	}

	Person(char *name, int age, char *work = "none") 
	{
		cout <<"Pserson(char*, int), name = "<<name<<", age= "<<age<<endl;
		this->age = age;

		this->name = new char[strlen(name) + 1];
		strcpy(this->name, name);

		this->work = new char[strlen(work) + 1];
		strcpy(this->work, work);
	}

	Person(Person &per) 
	{
		cout <<"Pserson(Person &)"<<endl;
		this->age = per.age;

		this->name = new char[strlen(per.name) + 1];
		strcpy(this->name, per.name);

		this->work = new char[strlen(per.work) + 1];
		strcpy(this->work, per.work);
	}

	~Person()
	{
		cout << "~Person()"<<endl;
		if (this->name) {
			cout << "name = "<<name<<endl;
			delete this->name;
		}
		if (this->work) {
			cout << "work = "<<work<<endl;
			delete this->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;
	}
};

class Student {
private:
	Person father;
	Person mother;
	int student_id;
public:
	Student()
	{
		cout<<"Student()"<<endl;
	}

	Student(int id, char *father, char *mother, int father_age = 40, int mother_age = 39) : mother(mother, mother_age), father(father, father_age)
	{
		cout<<"Student(int id, char *father, char *mother, int father_age = 40, int mother_age = 39)"<<endl;
	}

	~Student()
	{
		cout<<"~Student()"<<endl;
	}

	
};

int main(int argc, char **argv)
{
	Student s(100, "bill", "lily");  
	
	return 0;
}

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  • 原文地址：https://blog.csdn.net/weixin_50183638/article/details/126164101