String 类的函数实现

 1 #include<iostream>
 2 //#include<string>
 3 using namespace std;
 4 
 5 class Strings
 6 {
 7 public:
 8     Strings(const char * str=NULL);
 9     
10     Strings(const Strings &another);
11     ~Strings();
12     Strings & operator=(const Strings &ths);
13 private:
14     char *m_data;
15 };
16 Strings::Strings(const char *str)
17 {
18      if(str==NULL)
19      {
20       m_data=new char[1];
21       m_data[0]=‘\0‘;
22      }
23      else
24      {
25       m_data=new char[strlen(str)+1];
26       strcpy(m_data,str);
27      }
28 
29 }
30 Strings::Strings(const Strings &another)
31 {
32   m_data=new char[strlen(another.m_data)+1];
33   strcpy(m_data,another.m_data );
34 }
35 Strings::~Strings()
36 {
37 delete [] m_data;
38 }
39 
40 Strings &Strings::operator=(const Strings &ths)
41 {
42   if(this==&ths)
43       return *this;
44   delete[]m_data;
45   m_data=new char[strlen(ths.m_data)+1];
46   strcpy(m_data,ths.m_data);
47   return *this;
48 }
49 int main()
50 {
51   Strings a("abcdefg");
52   printf("%s\n",a);
53   Strings b(a);
54   printf("%s\n",b);
55   Strings c=b;
56   printf("%s\n",c);
57   system("pause");
58   return 0;
59 
60 }