C++ 为什么我得到的字符串没有命名类型错误？
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Why am I getting string does not name a type Error?
提问by Steven
game.cpp
游戏.cpp
#include <iostream>
#include <string>
#include <sstream>
#include "game.h"
#include "board.h"
#include "piece.h"
using namespace std;
game.h
游戏.h
#ifndef GAME_H
#define GAME_H
#include <string>
class Game
{
private:
string white;
string black;
string title;
public:
Game(istream&, ostream&);
void display(colour, short);
};
#endif
The error is:
错误是：
game.h:8 error: 'string' does not name a typegame.h:9 error: 'string' does not name a type
game.h:8 error: 'string' does not name a typegame.h:9 error: 'string' does not name a type
回答by Michael Mrozek
Your usingdeclaration is in game.cpp, not game.hwhere you actually declare string variables. You intended to put using namespace std;into the header, above the lines that use string, which would let those lines find the stringtype defined in the stdnamespace.
您的using声明位于 中game.cpp，而不是game.h您实际声明字符串变量的位置。您打算放入using namespace std;标题中，在 use 的行上方string，这将使这些行找到命名空间中string定义的类型std。
As others have pointed out, this is not good practicein headers -- everyone who includes that header will also involuntarily hit the usingline and import stdinto their namespace; the right solution is to change those lines to use std::stringinstead
正如其他人指出的那样，这在标头中并不是一个好习惯——每个包含该标头的人也会不由自主地点击该using行并导入std到他们的命名空间中；正确的解决办法是改变那些线使用std::string，而不是
回答by Johnsyweb
stringdoes not name a type. The class in the stringheader is called std::string.
string不命名类型。string标题中的类称为std::string。
Please do notput using namespace stdin a header file, it pollutes the global namespace for all users of that header. See also "Why is 'using namespace std;' considered a bad practice in C++?"
请不要放入using namespace std头文件，它会污染该头文件的所有用户的全局命名空间。另见“为什么是‘使用命名空间标准；’ 在 C++ 中被认为是一种不好的做法？”
Your class should look like this:
你的类应该是这样的：
#include <string>
class Game
{
private:
std::string white;
std::string black;
std::string title;
public:
Game(std::istream&, std::ostream&);
void display(colour, short);
};
回答by quamrana
Just use the std::qualifier in front of stringin your header files.
只需在头文件中使用std::前面的限定符string。
In fact, you should use it for istreamand ostreamalso - and then you will need #include <iostream>at the top of your header file to make it more self contained.
事实上，您应该将它用于istream和ostream- 然后您将需要#include <iostream>在头文件的顶部使其更加独立。
回答by Borealid
Try a using namespace std;at the top of game.hor use the fully-qualified std::stringinstead of string.
using namespace std;在顶部尝试 agame.h或使用完全限定的std::string而不是string。
The namespacein game.cppis after the header is included.
的namespace在game.cpp是被包括在报头之后。
