关于iOS下载中文文件路径及预览问题

不知道大家有没有遇到这样的情况，下载的文件文件名为中文，而iOS下载到本地，取response的suggestedFilename，但得到的却是é��åº�å¸�å·¥ä¼¤æ�¥é��ä½�é�¢ä¼�é£�è¡¥å�©è´¹ã��äº¤é��é£�å®¿è´¹å®¡æ ¸ç»�ç®�è¡¨.xls这样的乱码，WTF？而且使用UIDocumentInteractionController控件也无法预览（无法预览与名称编码有关，无法创建相应的路径）。

解决方案

自定义文件名

自己自定义文件名，比如20200909120808这种以时间戳当作文件名的。

编码解决

上面的方案的确可以解决问题，但是如果我就是想拿到文件本来的名字，比如文件是什么密钥，你随便起个名字，打开是一串数字，根本不知道是什么东西。
那么，我们需要知道究竟是什么原因造成了乱码，查了很久的资料，终于发现原来iOS，甚至MacOS上下载文件，文件名是ISO-8859-1编码 !!!!!
既然知道了是ISO编码这个关键信息，那就好办了，我们把它转换回来就行了，转换方法如下：

+ (NSString *)_859ToUTF8:(NSString *)oldStr
{
    NSStringEncoding enc = CFStringConvertEncodingToNSStringEncoding(kCFStringEncodingISOLatin1);

    return [NSString stringWithUTF8String:[oldStr cStringUsingEncoding:enc]];
}

image.png

通过上图，我们可以看到，确实是转换过来了。
那直接把转换后的字符串，当作文件名，我们发现，文件保存不了！！ why ? 买了否冷？
那肯定还是因为中文字符，我们做一下处理，如下代码为YYKit中NSString的分类中的方法

- (NSString *)stringByURLEncode {
    if ([self respondsToSelector:@selector(stringByAddingPercentEncodingWithAllowedCharacters:)]) {
        /**
         AFNetworking/AFURLRequestSerialization.m
         
         Returns a percent-escaped string following RFC 3986 for a query string key or value.
         RFC 3986 states that the following characters are "reserved" characters.
            - General Delimiters: ":", "#", "[", "]", "@", "?", "/"
            - Sub-Delimiters: "!", "$", "&", "'", "(", ")", "*", "+", ",", ";", "="
         In RFC 3986 - Section 3.4, it states that the "?" and "/" characters should not be escaped to allow
         query strings to include a URL. Therefore, all "reserved" characters with the exception of "?" and "/"
         should be percent-escaped in the query string.
            - parameter string: The string to be percent-escaped.
            - returns: The percent-escaped string.
         */
        static NSString * const kAFCharactersGeneralDelimitersToEncode = @":#[]@"; // does not include "?" or "/" due to RFC 3986 - Section 3.4
        static NSString * const kAFCharactersSubDelimitersToEncode = @"!$&'()*+,;=";
        
        NSMutableCharacterSet * allowedCharacterSet = [[NSCharacterSet URLQueryAllowedCharacterSet] mutableCopy];
        [allowedCharacterSet removeCharactersInString:[kAFCharactersGeneralDelimitersToEncode stringByAppendingString:kAFCharactersSubDelimitersToEncode]];
        static NSUInteger const batchSize = 50;
        
        NSUInteger index = 0;
        NSMutableString *escaped = @"".mutableCopy;
        
        while (index < self.length) {
            NSUInteger length = MIN(self.length - index, batchSize);
            NSRange range = NSMakeRange(index, length);
            // To avoid breaking up character sequences such as 👴🏻👮🏽
            range = [self rangeOfComposedCharacterSequencesForRange:range];
            NSString *substring = [self substringWithRange:range];
            NSString *encoded = [substring stringByAddingPercentEncodingWithAllowedCharacters:allowedCharacterSet];
            [escaped appendString:encoded];
            
            index += range.length;
        }
        return escaped;
    } else {
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wdeprecated-declarations"
        CFStringEncoding cfEncoding = CFStringConvertNSStringEncodingToEncoding(NSUTF8StringEncoding);
        NSString *encoded = (__bridge_transfer NSString *)
        CFURLCreateStringByAddingPercentEscapes(
                                                kCFAllocatorDefault,
                                                (__bridge CFStringRef)self,
                                                NULL,
                                                CFSTR("!#$&'()*+,/:;=?@[]"),
                                                cfEncoding);
        return encoded;
#pragma clang diagnostic pop
    }
}

调用方法后，便可正常的存储和预览分享了。

在此记录一下。