问题描述
嘿我正在寻找一种从另一个字符串中提取字符串的方法。它可以是任何长度并且位于字符串的任何部分,因此通常的方法不起作用。
Hey I am looking for a way to extract a string from another string. It could be any length and be in any part of the string so the usual methods don't work.
例如
我要提取的是从id =%到下一个%。
What I want to extract is from id=% to the next %.
任何想法都是?
推荐答案
使用rangeOfString方法:
Use the rangeOfString method:
NSRange range = [string rangeOfString:@"id=%"];
if (range.location != NSNotFound)
{
//range.location is start of substring
//range.length is length of substring
}
然后你可以使用 substringWithRange来切断字符串:
, substringFromIndex:
和 substringToIndex:
获取所需位的方法。以下是您特定问题的解决方案:
You can then chop up the string using the substringWithRange:
, substringFromIndex:
and substringToIndex:
methods to get the bits you want. Here's a solution to your specific problem:
NSString *param = nil;
NSRange start = [string rangeOfString:@"id=%"];
if (start.location != NSNotFound)
{
param = [string substringFromIndex:start.location + start.length];
NSRange end = [param rangeOfString:@"%"];
if (end.location != NSNotFound)
{
param = [param substringToIndex:end.location];
}
}
//param now contains your value (or nil if not found)
或者,这是从URL中提取查询参数的一般解决方案,如果您需要多次执行此操作,这可能更有用:
Alternatively, here's a general solution for extracting query parameters from a URL, which may be more useful if you need to do this several times:
- (NSDictionary *)URLQueryParameters:(NSURL *)URL
{
NSString *queryString = [URL query];
NSMutableDictionary *result = [NSMutableDictionary dictionary];
NSArray *parameters = [queryString componentsSeparatedByString:@"&"];
for (NSString *parameter in parameters)
{
NSArray *parts = [parameter componentsSeparatedByString:@"="];
if ([parts count] > 1)
{
NSString *key = [parts[0] stringByReplacingPercentEscapesUsingEncoding:NSUTF8StringEncoding];
NSString *value = [parts[1] stringByReplacingPercentEscapesUsingEncoding:NSUTF8StringEncoding];
result[key] = value;
}
}
return result;
}
这不会从值中删除%字符,但你可以做与
This doesn't strip the % characters from the values, but you can do that either with
NSString *value = [[value substringToIndex:[value length] - 1] substringFromIndex:1];
或类似
NSString *value = [value stringByReplacingOccurencesOfString:@"%" withString:@""];
更新: As iOS 8+的内置类是一个名为 NSURLComponents
的内置类,它可以自动为您解析查询参数( NSURLComponents
可用在iOS 7+上,但查询参数解析功能不是。)
UPDATE: As of iOS 8+ theres a built-in class called NSURLComponents
that can automatically parse query parameters for you (NSURLComponents
is available on iOS 7+, but the query parameter parsing feature isn't).
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