程序报错，请求帮忙看看，我头疼了。
首先我把错误的内容贴出来。
1.obj : error LNK2001: unresolved external symbol "class std::basic_istream<char,struct std::char_traits<char> > & __cdecl operator>>(class std::basic_istream<char,struct std::char_traits<char> > &,class String &)" (??5@YAAAV?$basic_istream@DU?$char
_traits@D@std@@@std@@AAV01@AAVString@@@Z)
Debug/wuyong5.exe : fatal error LNK1120: 1 unresolved externals
执行 link.exe 时出错.
wuyong5.exe - 1 error(s), 0 warning(s)
头文件内容
//.....................................................................................................................................
string1.h
#include <iostream>
using std::ostream;
using std::istream;
#ifndef STRING1_H_
#define STRING1_H_
class String
{
private:
char * str; // pointer to string
int len; // length of string
static int num_strings; // number of objects
//static int CINLIM = 80; // cin input limit
enum {CINLIM = 80};
public:
// constructors and other methods
String(const char * s); // constructor
String(); // default constructor
String(const String &); // copy constructor
~String(); // destructor
int length () const { return len; }
// overloaded operator methods
String & operator=(const String &);
String & operator=(const char *);
char & operator[](int i);
const char & operator[](int i) const;
// overloaded operator friends
friend bool operator<(const String &st, const String &st2);
friend bool operator>(const String &st1, const String &st2);
friend bool operator==(const String &st, const String &st2);
friend ostream & operator<<(ostream & os, const String & st);
friend istream & operator>>(istream & is, String & st);
// static function
static int HowMany();
};
#endif
//.............................................................................................................................
string1.cpp
#include <cstring> // string.h for some
#include "string1.h" // includes <iostream>
// using cin;
// using cout;
// initializing static class member
int String::num_strings = 0;
// static method
int String::HowMany()
{
return num_strings; //这是一个静态变量，计数。看有多少对象调用他了、
}
// class methods
String::String(const char * s) // construct String from C string
{
len = strlen(s); // 设置传入的字符长度。
str = new char[len + 1]; // 分配新的空间，空间长度为传进来的字符长度+1.为什么+1？
strcpy(str, s); // 拷贝字符串地址到空间。
num_strings++; //计数
}
String::String() // 默认的构造函数，不带参数
{
len = 4;
str = new char[1];
str[0] = '\0'; // default string
num_strings++;
}
String::String(const String & st)
{
num_strings++; // handle static member update
len = st.len; // same length
str = new char [len + 1]; // allot space
strcpy(str, st.str); // copy string to new location
}
String::~String() // necessary destructor
{
--num_strings; // required
delete [] str; // required
}
// overloaded operator methods
// assign a String to a String
String & String::operator=(const String & st)
{
if (this == &st)
return *this;
delete [] str;
len = st.len;
str = new char[len + 1];
strcpy(str, st.str);
return *this;
}
// assign a C string to a String
String & String::operator=(const char * s)
{
delete [] str;
len = strlen(s);
str = new char[len + 1];
strcpy(str, s);
return *this;
}
// read-write char access for non-const String
char & String::operator[](int i)
{
return str[i];
}
// read-only char access for const String
const char & String::operator[](int i) const
{
return str[i];
}
// overloaded operator friends
bool operator<(const String &st1, const String &st2)
{
return (strcmp(st1.str, st2.str) < 0);
}
bool operator>(const String &st1, const String &st2)
{
return st2.str < st1.str;
}
bool operator==(const String &st1, const String &st2)
{
return (strcmp(st1.str, st2.str) == 0);
}
// simple String output
ostream & operator<<(ostream & os, const String & st)
{
os << st.str;
return os;
}
//.............................................................................................................................
#include <iostream>
#include <cstdlib> // (or stdlib.h) for rand(), srand()
#include <ctime> // (or time.h) for time()
#include "string1.h"
const int ArSize = 10;
const int MaxLen = 81;
using namespace std;
int main()
{
String name;
cout <<"Hi, what's your name?\n>> ";
cin>>name;
cout << name << ", please enter up to " << ArSize
<< " short sayings <empty line to quit>:\n";
String sayings[ArSize];
char temp[MaxLen]; // temporary string storage
int i;
for (i = 0; i < ArSize; i++)
{
cout << i+1 << ": ";
cin.get(temp, MaxLen);
while (cin && cin.get() != '\n')
continue;
if (!cin || temp[0] == '\0') // empty line?
break; // i not incremented
else
sayings[i] = temp; // overloaded assignment
}
int total = i; // total # of lines read
if (total > 0)
{
cout << "Here are your sayings:\n";
for (i = 0; i < total; i++)
cout << sayings[i] << "\n";
// use pointers to keep track of shortest, first strings
String * shortest = &sayings[0]; // initialize to first object
String * first = &sayings[0];
for (i = 1; i < total; i++)
{
if (sayings[i].length() < shortest->length())
shortest = &sayings[i];
if (sayings[i] < *first) // compare values
first = &sayings[i]; // assign address
}
cout << "Shortest saying:\n" << * shortest << endl;
cout << "First alphabetically:\n" << * first << endl;
srand(time(0));
int choice = rand() % total; // pick index at random
// use new to create, initialize new String object
String * favorite = new String(sayings[choice]);
cout << "My favorite saying:\n" << *favorite << endl;
delete favorite;
}
else
cout << "Not much to say, eh?\n";
cout << "Bye.\n";
return 0;
}
//................................................................................................................................
测试后是cin>>name;的问题可能。。求解。
谢谢。
不要嫌弃分少，。感谢你。
[解决办法]
friend istream & operator>>(istream & is, String & st);
没定义吧
