截取URL中的参数

+ (NSString *)getParamValueFromUrl:(NSString *)url paramName:(NSString *)paramName

{

    if (![paramName hasSuffix:@"="]) {

        paramName = [NSString stringWithFormat:@"%@=", paramName];

    }

    

    NSString *str = nil;

    NSRange   start = [url rangeOfString:paramName];

    if (start.location != NSNotFound) {

        // confirm that the parameter is not a partial name match

        unichar  c = '?';

        if (start.location != 0) {

            c = [url characterAtIndex:start.location - 1];

        }

        if (c == '?' || c == '&' || c == '#') {

            NSRange     end = [[url substringFromIndex:start.location + start.length] rangeOfString:@"&"];

            NSUInteger  offset = start.location + start.length;

            str = end.location == NSNotFound ?

            [url substringFromIndex:offset] :

            [url substringWithRange:NSMakeRange(offset, end.location)];

            str = [str stringByRemovingPercentEncoding];

        }

    }

    return str;

}