//例18.32  实现真正的字符串赋值功能
#include <iostream>
using namespace std;
class String 
{
public:
	String();//默认构造函数用于创建空字符串
	String(const String&rs);
	String(const char*const ch);//带一个参数的构造函数用来初始化字符串
	char&operator[](unsigned short int length);
	char operator[](unsigned short int length)const;
    String&operator=(const String&s);//赋值函数用于两个字符串之间的赋值
	unsigned short int getlen()const{return len;}
	const char*getstr()const{return str;}
private:
	unsigned short int len;
	char*str;
};
String::String()
{
	cout<<"默认构造函数\n";
	len=0;
	str=new char[1];
	str[0]='\0';
}
String::String(const String&rs)
{
	cout<<"复制构造函数执行...\n";
	len=rs.getlen();
	str=new char[len+1];
	for(int i=0;i<len;i++)
		str[i]=rs[i];
	str[len]='\0';
}
String::String(const char*const ch)
{
	cout<<"构造函数\n";
	len=strlen(ch);
	str=new char[len+1];
	for(int i=0;i<len;i++)
		str[i]=ch[i];
	str[len]='\0';
}
char&String::operator[](unsigned short int length)
{
	cout<<"operator[]执行\n";
	if(length>len)
		return str[len-1];
	else
		return str[length];
}
char String::operator[](unsigned short int length)const
{
	cout<<"operator[]const执行\n";
	if (length>len)
	{
		return str[len-1];
	}
	else
		return str[length];
}
String&String::operator=(const String&s)
{
	cout<<"operator=执行...\n";
	if (this==&s)
		return *this;
	delete[]str;
	len=s.getlen();
	str=new char[len+1];
	for(int i=0;i<len;i++)
	{
		str[i]=s[i];
	}
	str[len]='\0';
	return *this;
}
int main()
{
	String s1="hello world";
	String s2;
	s2=s1;
	cout<<s2.getstr()<<endl;
	s2="name";
	cout<<s2.getstr()<<endl;
	return 0;
}