String类的构造与析构相关处理

String类原型：

 1 Class String
 2 {
 3 Public:
 4     String(const char *str);
 5     String(const String &other);
 6     ~String(void);
 7     String& operator =(const String &other);
 8 Private:
 9     char *m_data;
10 };

String的析构函数

1 String::~String(void)
2 {
3     delete []m_data;  //由于m_data是内部数据，也可以写成delete m_data;
4 }

String的构造函数

 1 String::String(const char *str)
 2 {
 3     if(str==NULL)
 4     {
 5         m_data = new char[1];
 6         *m_data = '\0';
 7     }
 8     else
 9     {
10         int length = strlen(str);
11         m_data = new char[length+1];
12         strcpy(m_data, str);
13     }
14 }

String的拷贝构造函数

1 String::String(const String &other)
2 {
3     int length = strlen(other.m_data);
4     m_data = new char[length+1];
5     strcpy(m_data, other.m_data);
6 }

String的拷贝赋值函数

 1 String& String::operator =(const String &other)
 2 {
 3     if(this==&other)
 4         return *this;
 5     int length = strlen(other.m_data);
 6     char *temp = new char[length+1];
 7     if(temp!=NULL)
 8     {
 9         strcpy(temp, other.m_data);
10         delete []m_data;
11         m_data = temp;
12     }
13     return *this;
14 }