如何保存/加载类型集？

问题描述

我有这个代码

type
  TXSample = (xsType1, xsType2, xsType3, xsType4, xsType5, xsType6, xsType6, xsTyp7, xsType8); // up to FXSample30;  
..

private
  FXSample = Set of TXSample;  
..

published
  property Sample: TXSample read FXSample  write FXSample; 
..

  //if Sample has a value of
  Sample := [xsType2, xsType4, xsType5, xsType6, xsTyp7];

我如何保存/加载Sample的属性？

i想保存在数据库中。

是可能的吗？

how can i save/load the property of Sample?
i would like to save it in the database.
is it possible?

推荐答案

如果您的设置永远不会超过32种可能性（ Ord（High（TXSample））），那么将集合类型转换为 Integer 并返回：

Provided your set will never exceed 32 possibilities (Ord(High(TXSample)) <= 31), then it is perfectly fine to typecast the set into an Integer and back:

type
  TXSamples = set of TXSample;
var 
  XSamples: TXSamples;
begin
  ValueToStoreInDB := Integer(XSamples);
  Integer(XSamples) := ValueReadFromDB;
end;

更具体地说： SizeOf（TXSamples）必须等于 SizeOf（StorageTypeForDB）。因此，当将 TXSamples 转换为：

To be more specific: SizeOf(TXSamples) has to be precisely equal to SizeOf(StorageTypeForDB). Thus the following ranges apply for Ord(High(TXSample)) when typecasting TXSamples to:

• 字节：Ord（高（TXSample））< 8


• Word：8< = Ord（High（TXSample））< 16


• 长字：16


• UInt64：32< = Ord（High（TXSample））< 64

• Byte: Ord(High(TXSample)) < 8
• Word: 8 <= Ord(High(TXSample)) < 16
• Longword: 16 <= Ord(High(TXSample)) < 32
• UInt64: 32 <= Ord(High(TXSample)) < 64

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