在数据集中存储Delphi集合的最佳方式是什么？ [英] What's the best way to store a Delphi set in a dataset?

问题描述

标题几乎说明了一切。我正在使用TClientDataset存储一个对象数组，其中一个对象有一个成员被定义为枚举类型的集合。据我所知，Delphi集是位域，它的大小可以从1到32个字节不等，取决于它们包含多少数据，Delphi没有定义一个TSetField。我应该使用什么类型的字段来加载这个值？

解决方案

您可以使用TBytesField或TBlobField

ClientDataSet1MySet：TBytesField，Size = 32

  var 
 MySet：set的字节
字节：字节数组; 
 begin 
 MySet：= [1，2，4，8，16]; 
 
 //写
 Assert（ClientDataSet1MySet.DataSize> = SizeOf（MySet），'数据字段太小'）; 
 
 SetLength（Bytes，ClientDataSet1MySet.DataSize）; 
 Move（MySet，Bytes [0]，SizeOf（MySet））; 
 ClientDataSet1.Edit; 
 ClientDataSet1MySet.SetData（@Bytes [0]）; 
 ClientDataSet1.Post; 
 
 //读取
 SetLength（Bytes，ClientDataSet1MySet.DataSize）; 
如果ClientDataSet1MySet.GetData（@Bytes [0]）then 
 Move（Bytes [0]，MySet，SizeOf（MySet））
 else 
 MySet：= []; // NULL 
 end; 
  

The title pretty much says it all. I'm using a TClientDataset to store an array of objects, and one of the objects has a member defined as a set of an enumerated type. As I understand it, Delphi sets are bitfields whose size can vary from 1 to 32 bytes depending on how much data they contain, and Delphi doesn't define a TSetField. What sort of field should I use to load this value into?

解决方案

You could use a TBytesField or a TBlobField

ClientDataSet1MySet: TBytesField, Size=32

var
  MySet: set of Byte;
  Bytes: array of Byte;
begin
  MySet := [1, 2, 4, 8, 16];

  // Write
  Assert(ClientDataSet1MySet.DataSize >= SizeOf(MySet), 'Data field is too small');

  SetLength(Bytes, ClientDataSet1MySet.DataSize);
  Move(MySet, Bytes[0], SizeOf(MySet));
  ClientDataSet1.Edit;
  ClientDataSet1MySet.SetData(@Bytes[0]);
  ClientDataSet1.Post;

  // Read
  SetLength(Bytes, ClientDataSet1MySet.DataSize);
  if ClientDataSet1MySet.GetData(@Bytes[0]) then
    Move(Bytes[0], MySet, SizeOf(MySet))
  else
    MySet := []; // NULL
end;

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