Destructor of member function

Definition ：

Destructor ： Contrary to constructor function , Destructors do not complete the destruction of objects , The destruction of local objects is done by the compiler . When the object is destroyed, it will automatically call the destructor , Complete some resource cleanup of the class

features ：

1. The destructor name is preceded by the character ~.
2. No parameter, no return value .
3. A class has only one destructor . If not explicitly defined , The system will automatically generate the default destructor .
4. At the end of the object's lifecycle ,C++ The compiler system automatically calls the destructor
For example , Let's look at the following code

typedef int DataType;
class SeqList
{
public:
	SeqList(int capacity = 10)
	{
		_pData = (DataType*)malloc(capacity * sizeof(DataType));
		assert(_pData);
		_size = 0;
		_capacity = capacity;
	}

private:
	int* _pData;
	size_t _size;
	size_t _capacity;
};

We all know that in general malloc After the space , We all need to use free To free up space .

And in practice , We sometimes overlook free, And run the code directly .

So for our convenience , Destructor here , It's equivalent to that the program automatically helps you make up one free come out .

Specific code ：

typedef int DataType;
class SeqList
{
public:
	SeqList(int capacity = 10)
	{
		_pData = (DataType*)malloc(capacity * sizeof(DataType));
		assert(_pData);
		_size = 0;
		_capacity = capacity;
	}
	~SeqList()
	{
		if (_pData)
		{
			free(_pData); //  Free up space on the heap 
			_pData = NULL; //  Set the pointer to null 
			_capacity = 0;
			_size = 0;
		}
	}

private:
	int* _pData;
	size_t _size;
	size_t _capacity;
};