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string类的构造和析构

class String

{

public:

  String(const char * str);

  String(const String & other);

  ~String();

  String& operator=(const String & other);

private:

  char * m_data;

}

 

String::~String()

{

  delete [] m_data;

}

 

String::String(const char * str)

{

  if(str == NULL)

  {

    m_data = http://www.mamicode.com/new char[1];

    m_data[0] = ‘\0‘;

  }

  else

  {

    int length = strlen(str);

    m_data = http://www.mamicode.com/new char[length + 1];

    strcpy(m_data, str);

  }

}

 

String::String(const String & other)

{

  int length = strlen(other.m_data);

  m_data = http://www.mamicode.com/new char[length + 1];

  strcpy(m_data, other.m_data);

}

 

String & String::operator=(const String & other)

{

  if(this == &other)

    return *this;  //如果地址相同时,直接返回

 

  delete [] m_data;  //释放原来的内存

  int length = strlen(other.m_data);

  m_data = http://www.mamicode.com/new char[length + 1];

  strcpy(m_data, other.m_data);

 

  return *this;

}

string类的构造和析构