自己实现String类

#include <iostream>
#include<string.h>

using namespace std;

class String
{
public:
String(const char *str = NULL);// 普通构造函数
String(const String &other);    // 拷贝构造函数
~String();    // 析构函数
String& operator=(const String &other);//赋值函数
bool operator==(const String &str);
friend ostream & operator<<(ostream& o,const String &str);
private:
char *m_data;// 用于保存字符串
};
//普通构造函数
String::String(const char *str)
{
if(str==NULL)
{
m_data = new char[1];//得分点：对空字符串自动申请存放结束标志'\0'
*m_data = '\0';
}
else
{
int length = strlen(str);
m_data = new char[length+1];//若能加 NULL 判断则更好
strcpy(m_data, str);
}
}
// String的析构函数
String::~String(void)
{
delete [] m_data; // 或delete m_data;
}
//拷贝构造函数
String::String(const String &other)//得分点：输入参数为const型
{
int length=strlen(other.m_data);
m_data=new char[length+1];//加分点：对m_data加NULL 判断
strcpy(m_data, other.m_data);
}
//赋值函数 重载=运算符
String & String::operator=(const String &other)//得分点：输入参数为const
{
if(this == &other)//得分点：检查自赋值
return *this;
delete [] m_data;//得分点：释放原有的内存资源
int length = strlen(other.m_data);
m_data = new char[length+1];//加分点：对m_data加NULL 判断
strcpy(m_data, other.m_data);
return *this;//得分点：返回本对象的引用
}
//重载==运算符
bool String::operator==(const String &str)
{
return strcmp(m_data, str.m_data)==0;
}
//重载<<运算符,使其可对传入的string对象进行输出
ostream & operator<<(ostream &o,const String &str)
{
o<<str.m_data;
return o;
}

int main()
{
String s = "hello";
String s2 = s;
String ss = "hello";
cout<<"s = "<<s<<endl;
cout<<"s2 = "<<s2<<endl;
bool flag=(ss==s2);
//boolalpha的作用是使bool型变量按照false、true的格式输出
cout<<boolalpha<<flag<<endl;
return 0;
}

s = hello
s2 = hello
true

Process returned 0 (0x0)   execution time : 1.109 s
Press any key to continue.