CODEWITHSUNDEEP
delphidelphi-xe2rtti
Brian Frost
Brian Frost

Reputation: 13454

Can I simplify this use of RTTI in delphi?

I'm doing some work with RTTI in Delphi XE3 and so far, this has resulted in a call to a procedure as follows:

procedure MyProc( ARecordInstance : pointer; ARecordType : PTypeInfo );

and I call this routine as follows:

MyProc( @MyRec TypeInfo( TMyRec ));

This all works fine.

It occurs to me that I might be able to simplify my procedure to:

procedure MyProc( var ARecord ); or procedure MyProc( ARecord : pointer );

..if I can get the type info from ARecord within my procedure. Working with an 'instance' such as 'ARecord' though, TypeInfo gives 'expects a type identifier' error, which is fair. Is there any way that I can pass a single pointer reference to my record and then extract the type from it?

Thanks

Upvotes: 3

Views: 495

Answers (2)

Arnaud Bouchez
Arnaud Bouchez

Reputation: 43023

Why not just code, with an un-typed var parameter:

procedure MyProc(var ARecordInstance; ARecordType : PTypeInfo);
begin
  ...

You will be able to call:

MyProc(MyRec,TypeInfo(TMyRec));

So avoid to type @MyRec. But you will also do not have strong type checking.

Using generics as proposed by Remy will allow strong typing, but will generate a bit more code.

Upvotes: 0

Remy Lebeau
Remy Lebeau

Reputation: 595295

If you need to support multiple types, you can wrap your procedure inside of a class that has a Generic parameter, then the procedure will know what data type it is working with, eg:

type
  MyClass<T> = class
  public
    class procedure MyProc(var AInstance : T);
  end;

class procedure MyClass<T>.MyProc(var AInstance : T);
var
  InstanceType: PTypeInfo;
begin
  InstanceType := TypeInfo(T);
  //...
end;

.

MyClass<TMyRec>.MyProc(MyRec);

Upvotes: 4

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