handle of object?

[slenkar]

is there any way to convert an object into an integer handle (or pointer)
and then convert it back?

I want to be able to serialize an object like this

type 
warrior=class(Tobject)
enemy:warrior

so I need to know.. when I save the warrior to a file, who his enemy is, so I need to convert the enemy to an integer handle, so I can serialize it
( I know you cant save handles to a file and then convert them back into objects when you load a new game, but they are useful to stop cyclic references when loading or saving a game)

[Brainer]

I'd declare a base class with methods to save/load an instance to a stream or a file. Or take a look at the TPersistent class.

[slenkar]

do you have a little example of saving an object with Tpersistent?

I tried running the example xmlstream in the lazarus folder but it says
streamasxmldemo.lpr(7,3) Fatal: Can't find unit Interfaces used by StreamAsXMLDemo

[User137]

Do you have latest Lazarus daily snapshot or SVN? I just added Interfaces in my uses path and it compiled fine.

[slenkar]

I managed to get the example running but the code is very long and uncommented

I put together a little program based on online examples:

program pascalreflect;

{$mode objfpc}{$H+}

uses
classes,typinfo;
 type

 warrior =class(Tobject)

 property
 name:String;
 hp:integer;
 end;
var
TypeInfo: PTypeInfo;
TypeData: PTypeData;
PropList: PPropList;
classref:Tclass;
war:warrior;
war2:warrior;
listy:array of string;
iter:integer;
{$IFDEF WINDOWS}{$R pascalreflect.rc}{$ENDIF}

begin
war:=warrior.create;


ClassRef := warrior.ClassType;

war2:=classref.newinstance as warrior;
//classname
writeln (classref.ClassName);
//typeinfo
TypeInfo := warrior.ClassInfo;
if typeinfo=nil then
begin
writeln('typeinfo is nil');
end
else
begin
TypeData := GetTypeData(TypeInfo);
end;




end.

typeinfo is null though

why is that?

[User137]

I have 1 guess; you are using .ClassInfo on type instead of war or war2 instances.
You can't do warrior.name:='test';

The next line seems also wrong:
lassRef := warrior.ClassType;
should be lassRef := war.ClassType;

For clarity i recommend using capital T in classnames, such as TWarrior. This makes it harder to mix classes with variable names.

[slenkar]

ok got a bit closer to getting the features I need to save a game

uses
  rttiutils,typinfo,classes;


type
  warrior =class(Tpersistent)
  public
  hp:integer;
  warname:string;
  published

   property Php:integer read hp write hp;
   property Pwarname:string read warname write warname;
    end;


Var
  O : warrior;
  PT : PTypeData;
  PI : PTypeInfo;
  I,J : Longint;
  PP : PPropList;
  prI : PPropInfo;

begin
  O:=warrior.Create;
  PI:=O.ClassInfo;
  PT:=GetTypeData(PI);
  Writeln('Property Count : ',PT^.PropCount);
  GetMem (PP,PT^.PropCount*SizeOf(Pointer));
  GetPropInfos(PI,PP);
  For I:=0 to PT^.PropCount-1 do
    begin
    With PP^[i]^ do
      begin
      Write('Property ',i+1:3,': ',name:30);
      writeln('  Type: ',typinfo.PropType(O,Name));
      end;
    end;
  FreeMem(PP);
  O.Free;
end.

[slenkar]

ok now i can get and set strings and integers without having to know the names of the fields.
getting closer to having a serialization library for pascal

Program pasreflect;

{ This program demonstrates the GetPropList function }

uses
  rttiutils,typinfo,classes,sysutils;


type
  warrior =class(Tpersistent)
  public
  hp:integer;
  warname:string;
  published

   property Php:integer read hp write hp;
   property Pwarname:string read warname write warname;
    end;


Var
  O : warrior;
  PT : PTypeData;
  PI : PTypeInfo;
  I,J : Longint;
  PP : PPropList;
  prI : PPropInfo;

begin
  O:=warrior.Create;
  PI:=O.ClassInfo;
  PT:=GetTypeData(PI);
  Writeln('Property Count : ',PT^.PropCount);
  GetMem (PP,PT^.PropCount*SizeOf(Pointer));
  GetPropInfos(PI,PP);
  For I:=0 to PT^.PropCount-1 do
    begin
    With PP^[i]^ do
      begin
      Write('Property ',i+1,': ',name);
      PrI:=GetPropInfo(O,name);
      if typinfo.PropType(O,Name)=tkinteger  then
      begin
      SetOrdProp(O,PrI,31);
      writeln('value'+ inttostr(GetOrdProp(O,PrI)));
      end;
      if typinfo.PropType(O,Name)=tksstring  then
      begin
      SetstrProp(O,PrI,'bill');
      writeln('value'+ (GetstrProp(O,PrI)));
      end;

      writeln('  Type: ',typinfo.PropType(O,Name));
      end;
    end;
  FreeMem(PP);


  writeln (inttostr(O.hp));

  O.Free;
end.

[slenkar]

I need a unique ID number for each object

I tried using the pointer address but the compiler said it wasnt portable
how else can I get a unique ID number for each object?

it has to be compatible with Tobject, as the serialization doesnt know the real object type.

I tried looking at the JSON library in lazarus.. is it cross platform?

[Brainer]

Below is a link you may find interesting. It's in Polish though. Try Google Translate or if you don't really need to understand the article's text, just focus on the code itself.
http://delphi.dathox.com/2009/12/ser...cz2-i-cz3.html