编写我自己的字符串类,但获取"引用'字符串'是不明确的"编译错误

Question

我正在尝试编写自己的字符串类(用于理解目的).我写了如下,文件1 string.h

#include<iostream>
#include<string.h>
namespace MyString
{
class string
{
char* ch;
int len;
public:
string();
string(const char* ch);
char* getString();
int length();
};
}

file 2 string.cpp

#include<iostream>
#include"string.h"
using namespace std;
using MyString::string; // use string from MyString namespace only.
string::string()
{                       
ch = NULL;      
len = 0;
}                     
string::string(const char* ch)
{                       
this->ch = ch;  
}   
char* string::getString()
{
return ch;
}
int string::length()
{
return len;
}
int main()
{
string obj = "This is a test";
cout << obj.getstring<<endl;
return 0;
}

但我的程序甚至无法编译,并出现以下错误

g++     string.cpp   -o string
string.cpp:6:1: error: reference to ‘string’ is ambiguous
string.h:5:8: error: candidates are: class MyString::string
/usr/include/c++/4.6/bits/stringfwd.h:65:33: error:                 typedef struct std::basic_string<char> std::string
string.cpp:6:1: error: ‘string’ does not name a type
string.cpp:12:1: error: reference to ‘string’ is ambiguous
string.h:5:8: error: candidates are: class MyString::string
/usr/include/c++/4.6/bits/stringfwd.h:65:33: error:                 typedef struct std::basic_string<char> std::string
string.cpp:12:1: error: ‘string’ does not name a type
string.cpp:23:7: error: reference to ‘string’ is ambiguous
string.h:5:8: error: candidates are: class MyString::string
/usr/include/c++/4.6/bits/stringfwd.h:65:33: error:                 typedef struct std::basic_string<char> std::string
string.cpp:23:7: error: reference to ‘string’ is ambiguous
string.h:5:8: error: candidates are: class MyString::string
/usr/include/c++/4.6/bits/stringfwd.h:65:33: error:                 typedef struct std::basic_string<char> std::string
string.cpp: In function ‘char* getString()’:
string.cpp:25:9: error: ‘ch’ was not declared in this scope
string.cpp: At global scope:
string.cpp:28:5: error: reference to ‘string’ is ambiguous
string.h:5:8: error: candidates are: class MyString::string
/usr/include/c++/4.6/bits/stringfwd.h:65:33: error:                 typedef struct std::basic_string<char> std::string
string.cpp:28:5: error: reference to ‘string’ is ambiguous
string.h:5:8: error: candidates are: class MyString::string
/usr/include/c++/4.6/bits/stringfwd.h:65:33: error:                 typedef struct std::basic_string<char> std::string
string.cpp: In function ‘int length()’:
string.cpp:30:9: error: ‘len’ was not declared in this scope
string.cpp: In function ‘int main()’:
string.cpp:35:2: error: reference to ‘string’ is ambiguous
string.h:5:8: error: candidates are: class MyString::string
/usr/include/c++/4.6/bits/stringfwd.h:65:33: error:                 typedef struct std::basic_string<char> std::string
string.cpp:35:9: error: expected ‘;’ before ‘obj’
make: *** [string] Error 1

我没有得到共鸣,为什么编译器使用MyNamespace中的字符串显式提供错误(即使用MyNamespace :: string;)？
这方面的任何指示都会非常有帮助.

Answer 1

你using namespace std在你的cpp文件里面.现在有一个字符串std和一个MySpace,所以编译器不知道选择哪一个.使用限定名称来区分它们,MyString::string而不是string删除using namespace std;OR将OR整个实现放入namespace MyString { ... }.