如我上一篇文章记录，我加了打开其他APPtxt文件的小功能，紧接着碰到新问题了，我在测试过程中发现用户上传的TXT编码格式很多不单单是utf-8和gb2312,针对TXT文档进行解码，我一共经历过两个阶段，如下

1.通过循环 解码不为空就返回字符串

  NSArray *encodings = @[
        @(NSUTF8StringEncoding),
        @(0x80000632),
        @(0x80000631),
        @(kCFStringEncodingGB_2312_80),
        @(kCFStringEncodingHZ_GB_2312),
        @(kCFStringEncodingMacChineseSimp),
        @(kCFStringEncodingDOSChineseSimplif),
        @(kCFStringEncodingGB_18030_2000),
        @(NSUTF16StringEncoding),
        @(NSUTF16LittleEndianStringEncoding),
        @(NSUTF16BigEndianStringEncoding),
        @(NSUTF32StringEncoding),
        @(NSUTF32LittleEndianStringEncoding),
        @(NSUTF32BigEndianStringEncoding)
    ];

    NSString *result = nil;
    for (NSInteger i = 0; i < encodings.count; i++) {
        unsigned int encoding = [encodings[i] unsignedIntValue];
        NSError *error = nil;
        NSString *content = [NSString stringWithContentsOfFile:filePath encoding:CFStringConvertEncodingToNSStringEncoding(encoding) error:&error];
        if (!error && !TJIsEmptyObject(content)) {
            result = content;
            break;
        }
    }
    return result;

此版本对于代码会碰到 编码成功 但是会是乱码的情况。

2.第二阶段 通过encodingOptions 进行处理

stringEncodingForData: encodingOptions: convertedString: usedLossyConversion 会自动挑选编码数组内合适的编码对字符串进行处理，目前尚未发现问题

    NSArray *encodings = @[
        @(NSUTF8StringEncoding),
        @(0x80000632),
        @(0x80000631),
        @(CFStringConvertEncodingToNSStringEncoding(kCFStringEncodingGB_2312_80)),
        @(CFStringConvertEncodingToNSStringEncoding(kCFStringEncodingHZ_GB_2312)),
        @(CFStringConvertEncodingToNSStringEncoding(kCFStringEncodingMacChineseSimp)),
        @(CFStringConvertEncodingToNSStringEncoding(kCFStringEncodingDOSChineseSimplif)),
        @(CFStringConvertEncodingToNSStringEncoding(kCFStringEncodingGB_18030_2000)),
        @(NSUTF16StringEncoding),
        @(NSUTF16LittleEndianStringEncoding),
        @(NSUTF16BigEndianStringEncoding),
        @(NSUTF32StringEncoding),
        @(NSUTF32LittleEndianStringEncoding),
        @(NSUTF32BigEndianStringEncoding)
    ];
   
         NSData * data = [NSData dataWithContentsOfFile:filePath];
         NSString * chapterContent = @"";
         BOOL lossy = NO;
          [NSString stringEncodingForData:data
         encodingOptions:@{NSStringEncodingDetectionSuggestedEncodingsKey:encodings}
         convertedString:&chapterContent  usedLossyConversion:&lossy];
 
    return chapterContent;

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