怎么实现String类的operator>>

[danny1221]

class String {
friend istream& operator>> ( istream& is, String& s ); // 如何实现
public:
String( );
String( const char* s );
String( const String& s );
~String( );
size_t length( ) const { return m_length; }
private:
char* m_data;
size_t m_length;
};

[ryfdizuo]

#include <iostream>
#include <string.h>
using namespace std;

#define SAFE_DELETE(p) { if(p!=0){delete p; p = NULL;}}
class String
{ 
	friend istream& operator>>  ( istream& is, String& s )
	{
		char cInput[128];
		is>>cInput;
		s.m_length=strlen(cInput);
		s.m_data=new char[s.m_length+1];
		strcpy(s.m_data, cInput);

		return is;
	}
	friend ostream& operator<<  ( ostream& os, String& s )
	{
		os<<s.m_data<<endl;
		return os;
	}
public: 
	String():m_data(NULL), m_length(0) 
	{}
	String( const char* s ):m_length(strlen(s)), m_data(NULL)
	{	
		m_data=new char[m_length+1];
		strcpy(m_data, s);
	}

	String( const String& s ):m_length(s.Getlength()), m_data(NULL)
	{
		m_data=new char[m_length+1];
		strcpy(m_data, s.m_data);
	}
	~String()
	{
		SAFE_DELETE(m_data);
		m_length=0;
	} 
	size_t Getlength() const { return m_length; } 
private: 
	char* m_data; 
	size_t m_length; 
};

int main()
{
	String test;
	cin>>test;
	cout<<test.Getlength()<<endl;
	cout<<test;
	return 0;
}

[Ronal_Lee]

这样就应该可以
istream &operator>>(istream &i, String &s)
{
	char str[100];
	i >> str;
	int length = strlen(str);
	delete s.m_cData;

	s.m_cData = new char[length+1];
	
	strcpy(s.m_cData, str);
	return i;
}

[Supper_Jerry]

friend istream& operator>> ( istream& is, String& s )
{
char cInput[128];
is>>cInput;
s.m_length=strlen(cInput);
if(s.m_data)
{
delete s.m_data;
s.data = NULL;
}、、应该需要delete一下吧
s.m_data=new char[s.m_length+1];
strcpy(s.m_data, cInput);

return is;
}

[danny1221]

istream& operator>> ( istream& is, String& s )
{
	const istream::sentry ok( is );
	if( ok ) {
		char c = is.rdbuf()->sgetc();
		size_t _size = UINT_MAX;
		s.make_empty( );
		
		for( ; 0 < _size && !is.eof(); --_size, c = is.rdbuf()->snextc() )
			if( isspace( c ) ) // skip whitespace
				break;
			else 
				s.append( c ); // 自己实现append
	}
	return is;
}

这是参考VC2008自带string的operator>>实现的超级简化版。
谢谢各位的回答。

[baihacker]

先放到一个数组里,然后计算长度,最后将s中以前的数据清理了,重新分配内存,并把数组里的数据copy进重新分配的内存...

[xbt746]

不知道，学习来的

[大爷想要时光机]

问题在于这个数组该设置多长呢？