如何使用bit/bit-operator来控制对象状态？

Question

我想创建轻型对象数据包以在客户端和服务器应用程序之间传递.

这是一个如此简单的任务,我只能控制1个字节,因此一个字节中的每个位都有不同的含义,

仅使用位

0 = False 
1 = True

Itens我现在需要:

1 - Loaded from database 
2 - Persisted
3 - Changed
4 - Marked to Delete
5 -
6 - 
7 - Null Value 
8 - Read Only


1) How do I use bit operators in Delphi to check each bit value? 
2) How do I set the bit Values?

解

在所有帮助之后,我会使用下一个Set

  TStateType = (
    stLoaded    = 0,   // loaded from persistance
    stNative    = 2,   // value loaded and converted to native type
    stPersisted = 3,   // saved
    stChanged   = 4,   // object or member changed
    stToDelete  = 5,   // marked to delete
    stReadOnly  = 6,   // read only object, will not allow changes
    stNull      = 7    // value is null
  );
  TState = Set of TStateType;

对于流 - >持久性,这将是要使用的记录:

  TDataPackage = record
    Data: TBytes;
    TypeInfo: TMetaInfo;
    State: Byte;
    Instance: TBuffer;
  end;

谢谢大家,感谢所有的答案和评论.

Answer 1

我真的为此使用了一套.但是,我看到你真的想要一个字节.在任何地方使用集合,然后在最后将类型转换为一个字节.

Barry Kelly指出,这种解决方案需要更少的打字,支持标准的delphi运营商并且不会带来任何性能损失.

procedure Test;
type
  TSetValues = (
    TSetValue1   = 0,
    TSetValue2   = 1,
    TSetValue4   = 2,
    TSetValue8   = 3,
    TSetValue16  = 4,
    TSetValue32  = 5,
    TSetValue64  = 6,
    TSetValue128 = 7
  );

  TMySet = set of TSetValues;
var
  myValue: byte;
  mySet: TMySet;
begin
  mySet := [TSetValue2, TSetValue16, TSetValue128];
  myValue := byte(mySet);
  ShowMessage(IntToStr(myValue)); // <-- shows 146
end;

Answer 2

我会用一套:

type
    TMyDatum = (mdLoaded, mdPersisted, mdChanged, mdMarkedToDelete, ...);
    TMyData = set of TMyDatum;

var
  Foo: TMyData;
begin 
  Foo := [mdLoaded, mdChanged];
  if (mdPersisted in Foo) then ...

它们以整数形式实现,因此您可以轻松地传递它们.我发现代码比按位运算符更容易读取.