IOS：NSString 从字符串中检索子字符串
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/8912146/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
IOS : NSString retrieving a substring from a string
提问by Burf2000
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.
嘿，我正在寻找一种从另一个字符串中提取字符串的方法。它可以是任意长度并且可以位于字符串的任何部分，因此通常的方法不起作用。
For example http://bla.com/bla?id=%1234%&something=%888%
例如 http://bla.com/bla?id=%1234%&something=%888%
What I want to extract is from id=% to the next %.
我要提取的是从 id=% 到下一个 %。
Any idea's?
有任何想法吗？
回答by Nick Lockwood
Use the rangeOfString method:
使用 rangeOfString 方法：
NSRange range = [string rangeOfString:@"id=%"];
if (range.location != NSNotFound)
{
//range.location is start of substring
//range.length is length of substring
}
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:
然后，您可以使用substringWithRange:,substringFromIndex:和substringToIndex:方法切碎字符串以获得所需的位。这是您的具体问题的解决方案：
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)
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:
或者，这里有一个从 URL 中提取查询参数的通用解决方案，如果您需要多次执行此操作，这可能更有用：
- (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;
}
This doesn't strip the % characters from the values, but you can do that either with
这不会从值中去除 % 字符，但您可以使用
NSString *value = [[value substringToIndex:[value length] - 1] substringFromIndex:1];
Or with something like
或者像
NSString *value = [value stringByReplacingOccurencesOfString:@"%" withString:@""];
UPDATE:As of iOS 8+ theres a built-in class called NSURLComponentsthat can automatically parse query parameters for you (NSURLComponentsis available on iOS 7+, but the query parameter parsing feature isn't).
更新：从 iOS 8+ 开始，有一个名为的内置类NSURLComponents可以为您自动解析查询参数（NSURLComponents在 iOS 7+ 上可用，但查询参数解析功能不可用）。
回答by Suraj K Thomas
Try this
尝试这个
NSArray* foo = [@"10/04/2011" componentsSeparatedByString: @"/"];
NSString* day = [foo objectAtIndex: 0];
NSArray* foo = [@"10/04/2011" componentsSeparatedByString: @"/"];
NSString* day = [foo objectAtIndex: 0];
