使用String :: Find函数

本文介绍了使用String :: Find函数的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述

我正在尝试在字符串中查找字符串，并且它不返回任何内容.....

I''m trying to find a string within a string and its not returning anything.....

if (client.SendHttpRequest()) { wstring httpResponseHeader = client.GetHttpResponseHeader(); string str ("wstring httpResponseHeader"); string str2 ("Content="); size_t found; found=str.find(str2); printf("\n%s\n\n",found); //wstring httpResponse = client.GetHttpResponse(); wprintf(L"HTTP Response Header:\n%s\n\n", httpResponseHeader.c_str()); //wprintf(L"HTTP Response:\n%s\n\n", httpResponse.c_str()); }

推荐答案

您期望找到什么?您搜索的字符串是"wstring httpResponseHeader"，并且您正在搜索不属于该字符串的"Content =.然后，将find成员函数的结果存储在变量found中.请注意，此值是位置值，在这种情况下将返回预定义的常量string::npos(顺便说一下，它不等于0). 但是，您没有从printf语句中看到任何有用结果的原因则完全不同:您提供了一个格式字符串，该字符串期望一个类型为string的变量(格式说明符为％s)，但是您提供了一个size_t类型的值，当然不适合.不幸的是，printf不会(实际上也不能)进行任何类型检查，因此它将尝试将string::npos转换为char指针，这当然会导致意外情况.啊，类型不安全的C函数的奇迹... 如果需要某种类型安全的输出，请使用iostrem，如下所示: What do you expect to find? The string your searching in is "wstring httpResponseHeader" and you''re searching for "Content=" which is not part of that string. Then you store the result of the find member function in the variable found. Note that this value is a position value, and in this case will return the predefioned constant string::npos (which by the way is not equal to 0). The reason you don''t see any useful result from your printf statement however is entirely different: you provide a format string that expects a variable of type string (format specifier %s), but you provide a value of type size_t, which of course doesn''t fit. Unfortunately printf does not (and in fact can not) do any type check, so it tries to convert string::npos into a char pointer, which of course results in something unexpected. Ahhh, the wonders of type-unsafe C functions... If you want some type-safe output, use iostrem, like this: #include <iostream> //... std::cout << std::endl << "find result: " << found << std::endl;

注意:std::endl等效于换行符；与``\ n''的主要区别是保证可以在任何操作系统上运行，包括需要额外的``\ r''(回车)的那些操作系统. PS:请查看以下内容: www.cplusplus/reference/string/string/find/ [ ^ ]

Note: std::endl is the equivalent of a line break; the main difference to ''\n'' is that it is guaranteed to work on any operating system, inlcuding those that require an additional ''\r'' (carriage return). P.S.: check this out: www.cplusplus/reference/string/string/find/[^]

您应该处理另一个爱好或学习编程的基础知识.给您买一本好书，或查看WorldWideWeb中的大量示例.为什么要从http协议开始?没有人会帮助您解决您的愚蠢重复问题. 问候. You should deal with another hobby or learning the basics of programming. Buy you a good book or check out the tons of examples in the WorldWideWeb. Why you are starting with http protocol? Nobody will help you with your stupid repeating questions. Regards.