栈中对象的生命周期

范围#

栈#

#include <iostream>  
#include <string>

class Entity
{
public:

	//constructor-构造函数
	Entity()
	{
		std::cout << "Created Entity!" << std::endl;
	}


	//destructor-析构函数
	~Entity()
	{
		std::cout << "Destroyed Entity!" << std::endl;
	}

};

int main()
{
	std::cout << "start--" << std::endl;
	{
		Entity e;
	}
	std::cout << "end--" << std::endl;
	std::cin.get();
}
/*
start--
Created Entity!
Destroyed Entity!
end--
*/

超出范围则自动销毁

堆#

#include <iostream>  
#include <string>

class Entity
{
public:

	//constructor-构造函数
	Entity()
	{
		std::cout << "Created Entity!" << std::endl;
	}


	//destructor-析构函数
	~Entity()
	{
		std::cout << "Destroyed Entity!" << std::endl;
	}

};

int main()
{
	std::cout << "start--" << std::endl;
	{
		Entity* e=new Entity();
	}
	std::cout << "end--" << std::endl;
	std::cin.get();
}
/*
start--
Created Entity!
end--
*/

返回栈内存的指针及解决办法#

#include <iostream>  
#include <string>

class Entity
{
public:

	//constructor-构造函数
	Entity()
	{
		std::cout << "Created Entity!" << std::endl;
	}


	//destructor-析构函数
	~Entity()
	{
		std::cout << "Destroyed Entity!" << std::endl;
	}

};

int* CreateArrayWrong()
{
	//在栈上声明一个数组
	//第一个元素为6，剩余49个为0
	int array[50] = { 6 };
	//返回指向该数组(栈内存)的指针
	return array;
}


int* CreateArray1()
{
	//在栈上声明一个数组
	//第一个元素为6，剩余49个为0
	int* array = new int[50] { 6 };
	//返回指向该数组(栈内存)的指针
	return array;
}
void CreateArray2(int*)
{
	//填充数组
}

int main()
{
	//错误,这里得到的数据是不可信的，
	//极有可能被其他代码拿来使用
	int* a = CreateArrayWrong();

	//方法1
	int* a1 = CreateArray1();
	//方法2
	int array[50];
	CreateArray2(array);

	std::cin.get();
}

智能指针#

这是一个包装类，构造在栈中使用指针，分配堆内存；在包装类销毁时删除指针

自己编写的简单版智能指针

#include <iostream>  
#include <string>

class Entity
{
public:

	//constructor-构造函数
	Entity()
	{
		std::cout << "Created Entity!" << std::endl;
	}


	//destructor-析构函数
	~Entity()
	{
		std::cout << "Destroyed Entity!" << std::endl;
	}

};

class ScopedPtr
{
private:
	Entity* m_Ptr;
public:
	ScopedPtr(Entity* ptr)
		:m_Ptr(ptr)
	{

	}

	~ScopedPtr()
	{
		delete m_Ptr;
	}
};

int main()
{
	std::cout << "start--" << std::endl;
	{
		//调用有参构造函数,隐式转换
		ScopedPtr e = new Entity();
		//Entity* e = new Entity();

	}
	std::cout << "end--" << std::endl;
	std::cin.get();
}
/*
start--
Created Entity!
Destroyed Entity!
end--
*/