c++ - fstream 和 ofstream
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c++ - fstream and ofstream
提问by Robin
What is the difference between:
有什么区别：
fstream texfile;
textfile.open("Test.txt");
and
和
ofstream textfile;
textfile.open("Test.txt");
Are their function the same?
它们的功能一样吗？
采纳答案by user657267
ofstreamonly has methods for outputting, so for instance if you tried textfile >> whateverit would not compile. fstreamcan be used for input and output, although what will work depends on the flags you pass to the constructor / open.
ofstream只有输出方法，所以例如如果你尝试textfile >> whatever它不会编译。fstream可用于输入和输出，尽管什么会起作用取决于您传递给构造函数 / 的标志open。
std::string s;
std::ofstream ostream("file");
std::fstream stream("file", stream.out);
ostream >> s; // compiler error
stream >> s; // no compiler error, but operation will fail.
The comments have some more great points.
评论有一些更重要的观点。
回答by Danqi Wang
Take a look at their pages on cplusplus.com hereand here.
在此处和此处查看他们在 cplusplus.com 上的页面。
ofstreaminherits from ostream. fstreaminherits from iostream, which inherits from both istreamand stream. Generally ofstreamonly supports output operations (i.e. textfile << "hello"), while fstreamsupports both output and input operations but depending on the flags given when opening the file. In your example, the open mode is ios_base::in | ios_base::outby default. The default open mode of ofstreamis ios_base::out. Moreover, ios_base::outis always set for ofstream objects (even if explicitly not set in argument mode).
ofstream继承自ostream. fstream继承自iostream，它继承自istream和stream。一般ofstream只支持输出操作（即 textfile << "hello"），同时fstream支持输出和输入操作，但取决于打开文件时给出的标志。在您的示例中，ios_base::in | ios_base::out默认情况下为打开模式。的默认打开方式ofstream是ios_base::out。此外，ios_base::out始终为 ofstream 对象设置（即使在参数模式下未明确设置）。
Use ofstreamwhen textfileis for output only, ifstreamfor input only, fstreamfor both input and output. This makes your intention more obvious.
使用ofstreamwhen textfileis for output only, ifstreamfor input only, fstreamfor both input and output. 这会让你的意图更加明显。
