Briefly about RTTI and attributes in Delphi 2010

RTTI (Runtime Type Information) was carefully reworked in Delphi 2010 .
RTTI is the central element on which the Delphi IDE is written, it has existed since the first release, however I have heard from some people over the years that they tried to use RTTI and found it too complex and complicated, especially compared to the Reflection API in Java and NET . This is a real shame, because the ability to write code to request detailed information about other objects, without knowing their type in advance, is a really powerful feature.

However, I think complaints will be a thing of the past with the new API . It was not only expanded, but became much more accessible and easy to use.

One of the new features that I am very impressed with is the support of attributes in the Win32 environment. I am working on a great example, but here we will quickly look at creating and then querying custom attributes.

Custom attributes are simply classes that are inherited from TCustomAttribute . They can have properties, methods, etc., like any other class:

MyAttribute = class(TCustomAttribute)
 private
  FName: string;
  FAge: Integer;
 public
  constructor Create(const Name : string; Age : Integer);
  property Name : string read FName write FName;
  property Age : Integer read FAge write FAge;
 end;

, .

:

TMyClass = class
 public
  [MyAttribute('Malcolm', 39)]
  procedure MyProc(const s : string);
  [MyAttribute('Julie', 37)]
  procedure MyOtherProc;
 end;

, . . , , , .

, , -, , API RTTI , ListBox:

procedure TForm3.Button1Click(Sender: TObject);
var
 ctx : TRttiContext;
 t : TRttiType;
 m : TRttiMethod;
 a : TCustomAttribute;
begin
 ListBox1.Clear;
 ctx := TRttiContext.Create;
 try
  t := ctx.GetType(TMyClass);
  for m in t.GetMethods do
   for a in m.GetAttributes do
    if a is MyAttribute then
     ListBox1.Items.Add(Format('Method = %s; Attribute = %s, Name = %s, Age = %d',
                  [m.Name, a.ClassName, MyAttribute(a).Name,
                   MyAttribute(a).Age]));
 finally
  ctx.Free;
 end;
end;

RTTI , ClassType . for..in , for..in . , , Name Age, ListBox.



, , , , , Delphi 2010.

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