C++ 在 Arduino 中将字符串转换为 const char*？
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String to const char* in Arduino?
提问by iosfreak
I have a variable tweetthat is a string and it has a character at the very beginning that I want to clip off.
我有一个tweet字符串变量，它在开头有一个我想剪掉的字符。
So what I want to do is use strstr()to remove it. Here's my code:
所以我想做的是用strstr()它来删除它。这是我的代码：
tweet = strstr(tweet, "]");
However, I get this error:
但是，我收到此错误：
cannot convert 'String' to 'const char*' for argument '1' to
'char' strstr(const char*, const char*)
So my thought would be to convert tweetinto a char. How would I go about doing so?
所以我的想法是转换tweet成一个字符。我该怎么做？
回答by David Grayson
How about you use substringinstead. This will be less confusing than converting between different types of string.
你换用怎么样substring。这将比在不同类型的字符串之间转换更容易混淆。
回答by Ernest Friedman-Hill
stringhas a c_str()member function that returns const char *.
string有一个c_str()返回的成员函数const char *。
回答by s3rius
you can do that easier. Since you're using C++:
你可以更轻松地做到这一点。由于您使用的是 C++：
tweet = tweet.substring(1);
substr() returns a part of the string back to you, as string. The parameter is the starting point of this sub string. Since string index is 0-based, 1 should clip off the first character.
substr() 将字符串的一部分作为字符串返回给您。参数是这个子串的起点。由于字符串索引是从 0 开始的，因此 1 应该剪掉第一个字符。
If you want to use strstr you can just cast tweet into a c-string:
如果您想使用 strstr ，您可以将推文转换为 c 字符串：
tweet = strstr( tweet.c_str(), "]" );
However, that's pretty inefficient since it returns a c-string which has to be turned into a std::string against in order to fit into tweet.
但是，这是非常低效的，因为它返回一个 c 字符串，必须将其转换为 std::string 以适应推文。
回答by alf
Using the following statement tweet.c_str()will return the string buffer, which will allow you to perform the edit you want.
使用以下语句tweet.c_str()将返回字符串缓冲区，这将允许您执行所需的编辑。
回答by pat1300
Look at:
看着：
string.indexOf(val)
string.indexOf(val, from)
Parameters
参数
string: a variable of type String
val: the value to search for - char or String
from: the index to start the search from
回答by Brian Chow
I realize this is an old question, but if you're trying to, say, compare a specific char, and not just one letter in a string, then what you want is string.charAt(n). For example, if you're doing serial programming and you need to check for STX (\02) than you can use the following code.
我意识到这是一个老问题，但是如果你想比较一个特定的字符，而不仅仅是字符串中的一个字母，那么你想要的是字符串.charAt(n)。例如，如果您正在进行串行编程并且需要检查 STX (\02)，则可以使用以下代码。
char STX = ''
if (inputString.charAt(0) == STX) {
doSomething();
}
