如何将ofstream用作结构体的一部分 – 函数参数。

huangapple
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英文:

How to use ofstream as a part of struct - arg of function

问题

I am trying to use ofstream, opened in function getlog() in function WriteLine(). I have a structure named LOG:

  1. 我试图在函数`getlog()`中打开的`ofstream`中使用它，而这个`LOG`结构是函数`WriteLine()`的参数。
  3. struct LOG {
  4.     wchar_t logfile[PARM_MAX_SIZE];
  5.     std::ofstream* stream;
  6. };

which is an argument of function WriteLine():
这是WriteLine()函数的一个参数：

When I am trying to use this stream, there is an error of reading:
当我尝试使用这个流时，出现了读取错误：

I am trying to use a reference on a LOG variable. I tried to convert ofstream* stream to ofstream& but I don't know how to do it properly, because initialization of a LOG is:

  1. 我试图使用`LOG`变量的引用。我尝试将`ofstream* stream`转换为`ofstream&`，但我不知道如何正确地做这件事，因为`LOG`的初始化是这样的：
  3. static const LOG INITLOG {L"", NULL};

and I don't know how to change it to use a reference on a stream:
而且我不知道如何更改它以使用流的引用：

Functions:
函数：

  1. LOG getlog(wchar_t logfile[]) {
  2.     ofstream logf(logfile, ios::app);
  3.     if (!logf.is_open()) {
  4.         throw ERROR_THROW(112)
  5.     }
  6.     LOG log{};
  7.     wcscpy_s(log.logfile, logfile);
  8.     log.stream = &logf;
  9.     return log;
  10. }
  12. void WriteLine(LOG log, char* c, ...) {
  13.     char str[80]{};
  14.     char** p = &c;
  15.     while (*p[0]) {
  16.         strcat_s(str, *p);
  17.         p++;
  18.     }
  19.     str[strlen(str)] = '
    LOG getlog(wchar_t logfile[]) {
  20.     ofstream logf(logfile, ios::app);
  21.     if (!logf.is_open()) {
  22.         throw ERROR_THROW(112)
  23.     }
  24.     LOG log{};
  25.     wcscpy_s(log.logfile, logfile);
  26.     log.stream = &logf;
  27.     return log;
  28. }
  30. void WriteLine(LOG log, char* c, ...) {
  31.     char str[80]{};
  32.     char** p = &c;
  33.     while (*p[0]) {
  34.         strcat_s(str, *p);
  35.         p++;
  36.     }
  37.     str[strlen(str)] = '\0';
  38.     ofstream* logf = log.stream;
  39.     *logf << "str";
  40. }
  41. ';
  42.     ofstream* logf = log.stream;
  43.     *logf << "str";
  44. }

main function:
主函数：

  1. int _tmain(int argc, wchar_t* argv[]) {
  2.     setlocale(LC_ALL, "rus");
  3.     Log::LOG log = Log::INITLOG;
  4.     try {
  5.         Parm::PARM parms = Parm::getparm(argc, argv);
  6.         log = Log::getlog(parms.log);
  7.         Log::WriteLine(log, (char*)"Тест:", (char*)" без ошибок \n", "");
  8.         /*Log::WriteLine(log, (wchar_t*)L"Тест:", (wchar_t*)L" без ошибок \n", L"");
  9.         Log::WriteLog(log);*/
  10.     }
  11.     catch (Error::ERROR e) {
  12.         cout << "Ошибка " << e.id << ": " << e.message << ", строка " << e.inext.line << ", позиция " << e.inext.col << endl << endl;
  13.     }
  15.     system("pause");
  16.     return 0;
  17. }
英文:

I am trying to use ofstream, opened in function getlog() in function WriteLine(). I have a structure named LOG:

  1. struct LOG {
  2. 	wchar_t logfile[PARM_MAX_SIZE];
  3. 	std::ofstream* stream;
  4. };

which is an argument of function WriteLine(). When I am trying to use this stream, there is an error of reading.

I am trying to use a reference on a LOG variable. I tried to convert ofstream* stream to ofstream&amp; but I don't know how to do it properly, because initialization of a LOG is:

  1. static const LOG INITLOG {L&quot;&quot;, NULL};

and I don't know how to change it to use a reference on a stream.

Functions:

  1. LOG getlog(wchar_t logfile[]) {
  2. 	ofstream logf(logfile, ios::app);
  3. 	if (!logf.is_open()) {
  4. 		throw ERROR_THROW(112)
  5. 	}
  6. 	LOG log{};
  7. 	wcscpy_s(log.logfile, logfile);
  8. 	log.stream = &amp;logf;
  9. 	return log;
  10. }
  12. void WriteLine(LOG log, char* c, ...) {
  13. 	char str[80]{};
  14. 	char** p = &amp;c;
  15. 	while (*p[0]) {
  16. 		strcat_s(str, *p);
  17. 		p++;
  18. 	}
  19. 	str[strlen(str)] = &#39;
    LOG getlog(wchar_t logfile[]) {
  20. ofstream logf(logfile, ios::app);
  21. if (!logf.is_open()) {
  22. throw ERROR_THROW(112)
  23. }
  24. LOG log{};
  25. wcscpy_s(log.logfile, logfile);
  26. log.stream = &amp;logf;
  27. return log;
  28. }
  29. void WriteLine(LOG log, char* c, ...) {
  30. char str[80]{};
  31. char** p = &amp;c;
  32. while (*p[0]) {
  33. strcat_s(str, *p);
  34. p++;
  35. }
  36. str[strlen(str)] = &#39;\0&#39;;
  37. ofstream* logf = log.stream;
  38. *logf &lt;&lt; &quot;str&quot;;
  39. }
  40. &#39;;
  41. 	ofstream* logf = log.stream;
  42. 	*logf &lt;&lt; &quot;str&quot;;
  43. }

main function

  1. int _tmain(int argc, wchar_t* argv[]) {
  2. 	setlocale(LC_ALL, &quot;rus&quot;);
  3. 	Log::LOG log = Log::INITLOG;
  4. 	try {
  5. 		Parm::PARM parms = Parm::getparm(argc, argv);
  6. 		log = Log::getlog(parms.log);
  7. 		Log::WriteLine(log, (char*)&quot;Тест:&quot;, (char*)&quot; без ошибок \n&quot;, &quot;&quot;);
  8. 		/*Log::WriteLine(log, (wchar_t*)L&quot;Тест:&quot;, (wchar_t*)L&quot; без ошибок \n&quot;, L&quot;&quot;);
  9. 		Log::WriteLog(log);*/
  10. 	}
  11. 	catch (Error::ERROR e) {
  12. 		cout &lt;&lt; &quot;Ошибка &quot; &lt;&lt; e.id &lt;&lt; &quot;: &quot; &lt;&lt; e.message &lt;&lt; &quot;, строка &quot; &lt;&lt; e.inext.line &lt;&lt; &quot;, позиция &quot; &lt;&lt; e.inext.col &lt;&lt; endl &lt;&lt; endl;
  13. 	}
  15. 	system(&quot;pause&quot;);
  16. 	return 0;
  17. }

答案1

得分: 0

Your getlog() function is creating a new stream and returning it, but is doing so by returning a pointer to a local variable that goes out of scope when the function exits. To avoid that, you will need to create the stream dynamically instead, eg:

  1. struct LOG {
  2.     std::wstring logfile;
  3.     std::unique_ptr<std::ofstream> stream;
  4. };
  6. LOG getlog(const wchar_t* logfile) {
  7.     LOG log;
  8.     log.logfile = logfile;
  9.     log.stream = std::make_unique<std::ofstream>(logfile, std::ios::app);
  10.     if (!log.stream->is_open()) {
  11.         throw ERROR_THROW(112)
  12.     }
  13.     return log;
  14. }
  16. template<typename... Args>
  17. void WriteLine(LOG& log, Args&&... args) {
  18.     (*(log.stream) << ... << args) << '\n';
  19. }
  21. int _tmain(int argc, wchar_t* argv[]) {
  22.     setlocale(LC_ALL, "rus");
  23.     try {
  24.         Parm::PARM parms = Parm::getparm(argc, argv);
  25.         Log::LOG log = Log::getlog(parms.log);
  26.         Log::WriteLine(log, "Тест:", " без ошибок ");
  27.         /*Log::WriteLine(log, L"Тест:", L" без ошибок ");
  28.         Log::WriteLog(log);*/
  29.     }
  30.     catch (Error::ERROR e) {
  31.         cout << "Ошибка " << e.id << ": " << e.message << ", строка " << e.inext.line << ", позиция " << e.inext.col << endl << endl;
  32.     }
  34.     std::system("pause");
  35.     return 0;
  36. }
英文:

Your getlog() function is creating a new stream and returning it, but is doing so by returning a pointer to a local variable that goes out of scope when the function exits. To avoid that, you will need to create the stream dynamically instead, eg:

  1. struct LOG {
  2.     std::wstring logfile;
  3.     std::unique_ptr&lt;std::ofstream&gt; stream;
  4. };
  6. LOG getlog(const wchar_t* logfile) {
  7.     LOG log;
  8.     log.logfile = logfile;
  9.     log.stream = std::make_unique&lt;std::ofstream&gt;(logfile, std::ios::app);
  10.     if (!log.stream-&gt;is_open()) {
  11.         throw ERROR_THROW(112)
  12.     }
  13.     return log;
  14. }
  16. template&lt;typename... Args&gt;
  17. void WriteLine(LOG&amp; log, Args&amp;&amp;... args) {
  18.     (*(log.stream) &lt;&lt; ... &lt;&lt; args) &lt;&lt; &#39;\n&#39;;
  19. }
  21. int _tmain(int argc, wchar_t* argv[]) {
  22.     setlocale(LC_ALL, &quot;rus&quot;);
  23.     try {
  24.         Parm::PARM parms = Parm::getparm(argc, argv);
  25.         Log::LOG log = Log::getlog(parms.log);
  26.         Log::WriteLine(log, &quot;Тест:&quot;, &quot; без ошибок &quot;);
  27.         /*Log::WriteLine(log, L&quot;Тест:&quot;, L&quot; без ошибок &quot;);
  28.         Log::WriteLog(log);*/
  29.     }
  30.     catch (Error::ERROR e) {
  31.         cout &lt;&lt; &quot;Ошибка &quot; &lt;&lt; e.id &lt;&lt; &quot;: &quot; &lt;&lt; e.message &lt;&lt; &quot;, строка &quot; &lt;&lt; e.inext.line &lt;&lt; &quot;, позиция &quot; &lt;&lt; e.inext.col &lt;&lt; endl &lt;&lt; endl;
  32.     }
  34.     std::system(&quot;pause&quot;);
  35.     return 0;
  36. }

huangapple
  • 本文由 发表于 2023年8月10日 19:25:05
  • 转载请务必保留本文链接：https://go.coder-hub.com/76875286.html
  • c++
  • pointers
  • reference
  • stream
  • struct
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