C++ 在头文件中使用未声明的标识符 (Clang)
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Use of undeclared identifier in header file (Clang)
提问by Axmill
I am creating a function to read the contents of a file, located in an IO.cpp file:
我正在创建一个函数来读取位于 IO.cpp 文件中的文件的内容：
#include "IO.h"
#include <iostream>
#include <fstream>
IO::IO()
{
//ctor
}
void IO::readFile(std::string fileName)
{
std::ofstream inputFile;
inputFile.open(FileName);
inputFile >> fileName.toStdString;
inputFile.close();
std::cout << fileName;
}
With the header file IO.h:
使用头文件 IO.h：
#ifndef IO_H
#define IO_H
class IO
{
public:
IO();
void readFile(std::string inputFile);
protected:
private:
};
#endif // IO_H
But I get an error from Clang that says
但是我从 Clang 收到一个错误，说
include/IO.h|9|error: use of undeclared identifier 'std'|
include/IO.h|9|错误：使用未声明的标识符“std”|
And I can't figure out how to solve it.
我不知道如何解决它。
回答by Luchian Grigore
When parsing the header (specifically the void readFile(std::string inputFile);line), the compiler doesn't know an stdnamespace exists, much less stringexists inside that namespace.
在解析标头（特别是void readFile(std::string inputFile);行）时，编译器不知道std命名空间存在，更不用说string存在于该命名空间内。
#include <string>in the header.
#include <string>在标题中。
