是否将枚举TagLib::ID3v2::AttachedPictureFrame::Type转换为字符串？

Question

我正在使用c++的标记库。如果我使用以下代码：

ID3v2::AttachedPictureFrame::Type t = picFrame->type();

例如，我得到了"FrontCover (3)"，但我没有找到任何解决方案来将其转换为字符串来保存值。

我还需要一个解决方案如何设置ID3v2::AttachedPictureFrame::Type t将其写入APIC标签。

Answer 1

TagLib::ID3v2::AttachedPictureFrame的文档说明Type是该类中定义的枚举：

枚举类型{其他= 0x00，FileIcon = 0x01，OtherFileIcon = 0x02，FrontCover = 0x03，BackCover = 0x04，LeafletPage = 0x05，媒体= 0x06，LeadArtist = 0x07，艺术家= 0x08，指挥家= 0x09，乐队= 0x0A，作曲家= 0x0B，词作者= 0x0C，RecordingLocation = 0x0D，DuringRecording = 0x0E，DuringPerformance = 0x0F，MovieScreenCapture = 0x10，ColouredFish = 0x11，插图= 0x12，BandLogo = 0x13，PublisherLogo = 0x14 }

没有自动转换来将enum的符号转换为std::string，反之亦然。另外，正如您注意到的，TagLib::ID3v2::AttachedPictureFrame类没有提供这样的功能。

为此，您需要实现助手函数：

std::string attachedPictureFrameType2String(AttachedPictureFrame::Type type) {
    switch(type) {
    case AttachedPictureFrame::Other: return "Other";
    case AttachedPictureFrame::FileIcon: return "FileIcon";
    case AttachedPictureFrame::OtherFileIcon: return "OtherFileIcon";
    case AttachedPictureFrame::FrontCover: return "FrontCover";
    // All the other enum values ...
    }
}

AttachedPictureFrame::Type string2AttachedPictureFrameType(const std::string& s) {
    if(s == "Other") return AttachedPictureFrame::Other;
    if(s == "FileIcon") return AttachedPictureFrame::FileIcon;
    if(s == "OtherFileIcon") return AttachedPictureFrame::OtherFileIcon;
    if(s == "FrontCover") return AttachedPictureFrame::FrontCover;
    // All the other valid string values ...
    throw std::exception("Invalid string");
}

正如@Uriya Harpeness在他们的comment中提到的，也可以使用字典来做到这一点，例如：

 using std::pair<AttachedPictureFrame::Type,std::string> = TypeDictItem;
 using std::vector<TypeDictItem> = TypeDict;
 const TypeDict pictureFrameTypeDict = { 
       std::make_pair(AttachedPictureFrame::Other,"Other")
     , std::make_pair(AttachedPictureFrame::FileIcon,"FileIcon")
     , std::make_pair(AttachedPictureFrame::OtherFileIcon,"OtherFileIcon")
     , std::make_pair(AttachedPictureFrame::FrontCover,"FrontCover")
     // ...
 };

 std::string attachedPictureFrameType2String(AttachedPictureFrame::Type type) {
     auto found = std::find_if(std::begin(pictureFrameTypeDict),
         std::end(pictureFrameTypeDict), 
         [type](const TypeDictItem& i) { return i.first == type; } );
     if(found != pictureFrameTypeDict.end()) {
          return (*found).second;
     }
     throw std::exception("Unexpected enum value.");
 }

 AttachedPictureFrame::Type string2AttachedPictureFrameType(const std::string s) {
     auto found = std::find_if(std::begin(pictureFrameTypeDict),
         std::end(pictureFrameTypeDict), 
         [s](const TypeDictItem& i) { return i.second == s; } );
     if(found != pictureFrameTypeDict.end()) {
          return (*found).first;
     }
     throw std::exception("Invalid string.");
 }