IOS:NSString从字符串中检索子字符串

Question

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.

例如 http://bla.com/bla?id=%1234%&something=%888%

我要提取的是从id =%到下一个%.

有任何想法吗？

Answer 1

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
}

然后,您可以用砍了绳子substringWithRange:,substringFromIndex:和substringToIndex:方法来得到你想要的位.这是您特定问题的解决方案:

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)

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:

- (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,但您可以使用

NSString *value = [[value substringToIndex:[value length] - 1] substringFromIndex:1];

或者类似的东西

NSString *value = [value stringByReplacingOccurencesOfString:@"%" withString:@""];

更新:从iOS 8+开始,调用内置类NSURLComponents可以自动为您解析查询参数(NSURLComponents在iOS 7+上可用,但查询参数解析功能不可用).