Class in Class/Osztály az osztályban (Multilang)
lazarus / 34-Windows

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TheProgrammer · 2011-08-20 16:50

How can i create Class in class?
Hogyan csinálhatok osztályt az osztályban?

Example/Példa:
Code: [Select]type
  TClassInClass = class
    var1, var2, var3 : String;
  end;

  TMyClass = class
    ClassInClass  : TClassInClass;
    function classfunction : Boolean;
    procedure classprocedure(const const1, const2, const3 :
WideString);
  end; 

or/vagy

Code: [Select]type
  TCecordInClass = record
    var1, var2, var3 : String;
  end;

  TMyClass = class
    CecordInClass : TCecordInClass;
    function classfunction : Boolean;
    procedure classprocedure(const const1, const2, const3 :
WideString);
  end;
These codes don't work...
Ez a kód nem működik...

Error: Project xy raised exception class 'External:SIGSEGV'.

My System setting: Windows 7 32bit / Lazarus 0.9.30 and FPC 2.4.2

This is Unit file, not program...
Ez itt modul, nem program kód...

Mode: {$mode objfpc}{$H+}
My Uses list:
Ezeket a forrásokat használom:
Classes, SysUtils, Math, ActiveX, ComObj, Variants;

(I use Ole WMI function...)
(WMI Ole funkciót használok...)
Code: [Select]
procedure TMyClass.classprocedure(const const1, const2, const3 :
WideString);
begin
ClassInClass.Var := FWbemObject.Properties_.Item('L2CacheSize').Value;
end;

All Code run in TThread class in Program...
AZ összes kód egy Programszál osztályban fut...

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Leledumbo · 2011-08-20 16:59

The problem is not class in class (because it passes compiling step
and generates executable), but how you use it.
QuoteClassInClass.Var :=
FWbemObject.Properties_.Item('L2CacheSize').Value;Have you initialized
ClassInClass?

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TheProgrammer · 2011-08-20 17:08

I defined "ClassInClass" in type and I'd like to add value in
"MyClass" procedure...
Definiáltam a típusoknál a "ClassInClass"-t és szeretnék adni neki egy
értéket a "MyClass" procedurájában...

Defined: see examples...
Definíció: lásd példa....

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TheProgrammer · 2011-08-20 17:16

QuoteClassInClass.Var :=
FWbemObject.Properties_.Item('L2CacheSize').Value;Correction:
Javítás:
ClassInClass.Var1 :=
FWbemObject.Properties_.Item('L2CacheSize').Value;

I would like to do this in program:
Ezt szeretném elérni a programban:

MyClass.classprocedure('xy', 'xy', 'xy');

Label.Caption := MyClass.ClassInClass.Var1

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Arbee · 2011-08-20 17:36

What Leledumbo refers to is whether you have created an instance of
ClassInClass, which would normally be done in the constructor of
TMyClass.  Without it you will definitely get a SIGSEGV.

If you also get the SIGSEGV when using a Record, then it suggests the
real issue is with the FWemObject.  Is that properly instantiated?

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JD · 2011-08-20 17:41

I assume that you are familiar with associative classes & composite
classes. If not read this
http://delphi.about.com/od/course/a/delphi_oop19.htm

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TheProgrammer · 2011-08-20 17:46

Quote from: Arbee on August 20, 2011, 07:36:52 pmIs that properly
instantiated?

Quote from: Leledumbo on August 20, 2011, 06:59:42 pmHave you
initialized ClassInClass?

How can i initalised the ClassInClass? This part I do not know...
Hogyan tudok inicializálni? Ezt a részét nem ismerem...

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TheProgrammer · 2011-08-20 17:54

I have to do "ClassInClass" variables in "Implementation" section?
<-This by Google Translation
Kell csinálnom "ClassInClass" változókat az "Implementation" részhez?

Sorry, My English translation is not perfect...

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JD · 2011-08-20 18:26

You can initialize TClassInClass in 2 places

a) inside the constructor of TMyClass. TMyClass will then be a
composite class. TMyClass will then own TClassInClass.

b) elsewhere in the program. TMyClass will then be associated with
TClassInClass & the two can have independent lifespans.

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Carver413 · 2011-08-20 19:09

When you declare a class in a class you end up with a nil pointer that
represents where the class should go. only after you assign it
Code: [Select]  CecordInClass:= TCecordInClass.Create;
will the class actually exist.
to do this properly you should declaire two function
Code: [Select]Procedure TMyClass.AfterConstruction;
begin
  CecordInClass:= TCecordInClass.Create;
end;
Procedure TMyClass.BeforeDestruction;
begin
  CecordInClass.Destroy;
end;
  These are declare it TObject so you will need to add override to
your  declaration
Code: [Select]TMyClass = class
    CecordInClass : TCecordInClass;
    Procedure BeforeDestruction; override;
    Procedure AfterConstruction; override;
    function classfunction : Boolean;
    procedure classprocedure(const const1, const2, const3 :
WideString);
  end;

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TheProgrammer · 2011-08-20 21:10

Thanks for All!Köszönöm a segítséget!

This is my solution 1:
1. megoldásom:
Code: [Select]//Unit:
   TRecordInClass = record
     Var1, Var2 : String;
   end;

  TMyClass = class
    RecordInClass : TRecordInClass;
    constructor Create;
  end;


constructor TMyClass.Create;
begin
RecordInClass.Var1 := 'xy';
RecordInClass.Var2 := 'yx';
end;

//----------
//Program:
procedure TForm1.Button1Click(Sender: TObject);
begin
MyClass := TMyClass.Create;
Label1.Caption := MyClass.RecordInClass.Var1;
MyClass.Destroy; 
end;

This is my solution 2:
2. megoldásom:
Code: [Select]//Unit:
   TClassInClass = Class
     Var1, Var2 : String;
     //Other
   end;

  TMyClass = class
    ClassInClass : TClassInClass;
    constructor Create;
    destructor Destroy;
  end;


constructor TMyClass.Create;
begin
ClassInClass := TClassInClass.Create;

ClassInClass.Var1 := 'xy';
ClassInClass.Var2 := 'yx';
end;

destructor TMyClass.Destroy;
begin
ClassInClass.Destroy;
end;

//----------
//Program:
procedure TForm1.Button1Click(Sender: TObject);
begin
MyClass := TMyClass.Create;
Label1.Caption := MyClass.ClassInClass.Var1;
MyClass.Destroy;
end;

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Carver413 · 2011-08-20 21:39

do not forget that which you create you must also destroy

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TheProgrammer · 2011-08-20 23:03

Ok  I write Destroy/destructor code...
Oké  Írok lezáró részeket (Destroy)...