XCode：摆脱警告“未知转义序列\+”
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XCode: Getting rid of warning "Unknown escape sequence \+"
提问by toom
In my code I make extensive use of regular expression, and my patterns look something like this
在我的代码中，我广泛使用了正则表达式，我的模式看起来像这样
regexp = [[NSRegularExpression alloc] initWithPattern:@".*?\\+.*?\\+.*?\\+.*?\\+.*?\\+.*?\\+" options:0 error:nil];
For the escape sequences I get compiler warnings like "Unknown escape sequence +" which is extremely annoying because it is not wrong in my case. How can I get rid of this warning?
对于转义序列，我收到诸如“未知转义序列 +”之类的编译器警告，这非常烦人，因为在我的情况下这并没有错。我怎样才能摆脱这个警告？
回答by zaph
You have to many back-slash characters, use:
您必须使用许多反斜杠字符，请使用：
regexp = [[NSRegularExpression alloc] initWithPattern:@".*?\+.*?\+.*?\+.*?\+.*?\+.*?\+" options:0 error:nil];
To get a \in a string it needs to be escaped: \\. So \\\+applies the first \to escaping the second \and the third \tries to escape the plus sign +which is an illegal escape.
要\在字符串中获取 a需要对其进行转义：\\。因此\\\+将第一个\应用于转义第二个\，第三个\尝试转义加号+，这是非法转义。
