Pascal 对象：如何进行类型化前向声明？
我正在将很棒的 fmod C 标头翻译为 Pascal，但由于前向声明而陷入困境。 如果我在类型之前声明函数，则错误为“FMOD_CODEC_STATE：未知”，如果我在函数之前声明FMOD_CODEC_STATE，则错误为“FMOD_CODEC_METADATACALLBACK：未知” 知道我该如何解决这个问题吗？ 非常感谢 ！
type
FMOD_CODEC_STATE = Record
numsubsounds: Integer;
waveformat: array[0..0] of FMOD_CODEC_WAVEFORMAT;
plugindata: Pointer;
filehandle: Pointer;
filesize: Cardinal;
fileread: FMOD_FILE_READCALLBACK;
fileseek: FMOD_FILE_SEEKCALLBACK;
metadata: FMOD_CODEC_METADATACALLBACK;
end;
FMOD_CODEC_METADATACALLBACK = function (codec_state: FMOD_CODEC_STATE; tagtype: FMOD_TAGTYPE; name: PChar; data: Pointer; datalen: Cardinal; datatype: FMOD_TAGDATATYPE; unique: Integer):FMOD_RESULT;
I'm translating the great fmod C header to Pascal, and I'm stuck because of a forward declaration.
If I declare the function before the type, the error is "FMOD_CODEC_STATE: unknown", and if I declare the FMOD_CODEC_STATE before the function, the error is "FMOD_CODEC_METADATACALLBACK: unknown"
Any idea how I could solve this problem?
Thank you very much !
type
FMOD_CODEC_STATE = Record
numsubsounds: Integer;
waveformat: array[0..0] of FMOD_CODEC_WAVEFORMAT;
plugindata: Pointer;
filehandle: Pointer;
filesize: Cardinal;
fileread: FMOD_FILE_READCALLBACK;
fileseek: FMOD_FILE_SEEKCALLBACK;
metadata: FMOD_CODEC_METADATACALLBACK;
end;
FMOD_CODEC_METADATACALLBACK = function (codec_state: FMOD_CODEC_STATE; tagtype: FMOD_TAGTYPE; name: PChar; data: Pointer; datalen: Cardinal; datatype: FMOD_TAGDATATYPE; unique: Integer):FMOD_RESULT;
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记录不需要按值传递。事实上，原始的 C 代码无论如何都不会按值传递它。它是通过引用传递的，带有指针。声明指针，然后声明函数，然后声明记录：
是的，您可以在声明它指向的对象之前声明指向某个对象的指针。但是，您不允许前向声明记录，因此上面给出的顺序是这三个声明的唯一可能的顺序。
The record doesn't need to be passed by value. In fact, the original C code doesn't pass it by value anyway. It's passed by reference, with a pointer. Declare the pointer, then the function, and then the record:
Yes, you're allowed to declare a pointer to something before you've declared the thing it points to. You're not allowed to forward-declare records, though, so the order given above is the only possible order for those three declarations.
Pascal 对指针类有自动前向类型声明，这就是我假设函数实际采用的类型声明。因此，只需将您的声明更改为类似以下内容（警告，我已经超过 12 年没有使用过 pascal）应该可以工作：
Pascal has automatic forward type declaration for pointer classes, which is what I'm assuming that function actually takes. So simply changing your declarations to something like this (warning, I haven't used pascal in over 12 years) should work: