ios无法识别
我正在开发一个执行 fileIO 的 Windows VC++2008 程序，并且遇到了一个非常奇怪的问题。在我的 #include 指令中，我有
#include "stdafx.h"
#include <iostream>
#include <fstream>
#include <string>
一个实际上执行 fileIO 的方法，但是当我尝试像这样打开文件时：
std::ofstream Output;
Output.open("Output/log.txt", ios::out);
我的 intelisense 允许它，甚至有正确的自动完成，但我的编译器抛出错误：
1>c:...\engine\gsp420maincore\gsp420maincore\messagequeue.cpp(141) : error C2653: 'ios' : is not a class or namespace name
1>c:...\engine\gsp420maincore\gsp420maincore\messagequeue.cpp(141) : error C2065: 'out' : undeclared identifier
当我读到 ofstream.open() 时，它指出要打开的文件是否用于输入、输出或两者都应指定，但 ios 应该由任何其他 iostream #include 指令自动包含，并且这个问题不是当我插入时更正：
#include <ios> // directive
当我删除第二个参数时，编译器没有任何抱怨，但我知道我应该尝试并指定，以防万一我想进入并从文件中读取以及写入文件。我做错了什么吗？
I am working on a Windows VC++2008 program that does fileIO, and have hit an issue that is really weird. in my #include directives I have
#include "stdafx.h"
#include <iostream>
#include <fstream>
#include <string>
and then I have a method that actually does the fileIO, but when I try to open the file like this:
std::ofstream Output;
Output.open("Output/log.txt", ios::out);
my intelisense allows it, and even has correct auto completes, but my compiler throws an error of:
1>c:...\engine\gsp420maincore\gsp420maincore\messagequeue.cpp(141) : error C2653: 'ios' : is not a class or namespace name
1>c:...\engine\gsp420maincore\gsp420maincore\messagequeue.cpp(141) : error C2065: 'out' : undeclared identifier
when I read about the ofstream.open() it stated that whether the file to be opened is for input, output, or both should be specified, but ios should be automatically included by any other iostream #include directive, and this problem is not corrected when I insert the:
#include <ios> // directive
the compiler has no complaints when I remove the second argument, but I know that I should try, and specify just in case I want to go in and read from a file as well as write to it. did I do something wrong?
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看起来您忘记在它前面加上
std::前缀，并且没有使用using namespace std;（从您明确声明的命名空间这一事实来看>std::ofstream）。尝试将其更改为
std::ios::out。您不需要手动
#include。It looks like you forgot to prefix it with
std::and you haven't usedusing namespace std;(judging from the fact that you explicitly state the namespace forstd::ofstream).Try changing it to
std::ios::out.You should not need to
#include <ios>manually.正如已经指出的，您需要
std::ios::out——只是您根本不需要它。当您打开ofstream时，它会默认打开以进行输出（同样，默认情况下会打开ifstream以进行输入）。我还建议在创建时初始化对象，而不是创建某种未初始化的流，然后单独打开它。考虑到这一点，您会得到相当简单的代码：As already noted, you need
std::ios::out-- only you really don't need it at all. When you open anofstream, it opens for output by default (likewise, anifstreamgets opened for input by default). I'd also advise initializing the object at creation rather than creating a sort-of uninitialized stream, then opening it separately. Taking that into account, you get rather simpler bit of code: