什么是现代当量（C ++）风格为老（C类）的fscanf方法？ [英] What is the modern equivalent (C++) style for the older (C-like) fscanf method?

问题描述

什么是最好的选择，如果我想升级老C- code到新的C ++读书用分号分隔符的文件时：

  / *从文件C类阅读：* /
的fscanf（tFile，％D，＆安培; mypost.nr）; / *分隔符; * /
的fscanf（tFile;％[^];，mypost.aftername）; / *定界符; * /
的fscanf（tFile，％[^;]，mypost.forename）; / *分隔符; * /
的fscanf（tFile;％[^];，mypost.dept）; / *定界符; * /
的fscanf（tFile，％[^];，mypost.position）; / *定界符; * /
的fscanf（tFile，％D，＆安培; mypost.nr2）;// eqivalent最好的C ++实现的方法同样的事情？
 

解决方案

您可以在超载的的IStream右移位运算符的结构，所以：

 的std :: istream的＆安培;运营商的GT;＆GT;（的std :: istream的＆放大器是，mypost_struct＆安培; MPS）{
    是＆GT;＆GT; mps.nr;
    is.ignore（1，';'）;
    is.getline（mps.forename，255，';'）;
    is.getline（mps.aftername，255，';'）;
    是＆GT;＆GT; mps.dept;
    is.ignore（1，';'）;
    是＆GT;＆GT; mps.position;
    is.ignore（1，';'）;
    是＆GT;＆GT; mps.nr2;    回报;
}
 

随后，输入为简单的＆GT;＆GT; mypost; ，其中是是你已经打开的文件

编辑：@UncleBens感谢指出了这一点，我忘了带空间帐户。我已经更新了答案，假设名字及aftername可能包含空格。还有是关于分隔符是双引号的这个相当embarrasing位...

我只是检查它使用的是结构定义为下：

 结构mypost_struct {
    INT NR;
    焦炭用的名字[255]，aftername [255];
    INT部门，职位，NR;
};
 

..和结果符合市场预期。

What is the best option if I want to "upgrade" old C-code to newer C++ when reading a file with a semicolon delimiter:

/* reading in from file C-like: */
fscanf(tFile, "%d", &mypost.nr); /*delimiter ; */
fscanf(tFile, " ;%[^;];", mypost.aftername);/* delimiter ; */
fscanf(tFile, " %[^;]", mypost.forename);   /*delimiter ; */
fscanf(tFile, " ;%[^;];", mypost.dept);/*delimiter ; */
fscanf(tFile, " %[^;];", mypost.position);/* delimiter ; */
fscanf(tFile, "%d", &mypost.nr2);

//eqivalent best C++ method achieving the same thing?

解决方案

You could overload the right-shift operator on istream for your struct, so:

std::istream& operator>>(std::istream& is, mypost_struct& mps) {
    is >> mps.nr;
    is.ignore(1, ';');
    is.getline(mps.forename, 255, ';');
    is.getline(mps.aftername, 255, ';');
    is >> mps.dept;
    is.ignore(1, ';');
    is >> mps.position;
    is.ignore(1, ';');
    is >> mps.nr2;

    return is;
}

Subsequently, input is as simple as is >> mypost;, where is is the file that you have opened.

Edit: @UncleBens Thanks for pointing this out, I had forgotten to take spaces in account. I have updated the answer, assuming that forename and aftername are likely to contain spaces. And there was this rather embarrasing bit about the delimiters being double-quoted...

I just checked it using a struct definition as under:

struct mypost_struct {
    int nr;
    char forename[255], aftername[255];
    int dept, position, nr2;
};

.. and the result was as expected.

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