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Is it possible to restrict access on structure fields?
Posted: Fri Sep 08, 2023 1:02 am
by jacdelad
Hi,
is this possible? Let's say I have a Structure, defined in a module:
Code: Select all
Structure Gerber
Identification.q
BoardSize.Pos;in mm
DrawScaling.f
Unit.a;mm/inch
EndStructure
...and I want to prevent the programmer from having access to the DrawScaling variable outside the unit. Is this possible? Or do I need a second structure which is completely put inside the module and a mapping/assignment mechanism inside the module? I hope I can express my question correctly...
Re: Is it possible to restrict access on structure fields?
Posted: Fri Sep 08, 2023 4:33 am
by Cyllceaux
I have some Ideas:
Idea 1:
Code: Select all
DeclareModule Test
Structure Pos
X.i
Y.i
EndStructure
Structure Gerber
Identification.q
BoardSize.Pos;in mm
Unit.a ;mm/inch
EndStructure
EndDeclareModule
Module Test
Structure InternGerber Extends Gerber
DrawScaling.f
EndStructure
EndModule
Idea 2:
Code: Select all
DeclareModule Test2
Interface Gerber
GetIdentification.q():SetIdentification(value.q)
GetBoardSizeX():SetBoardSizeX(value)
GetBoardSizeY():SetBoardSizeY(value)
GetUnit.a():SetUnit(value.a)
EndInterface
Declare create()
EndDeclareModule
Module Test2
Structure Pos
X.i
Y.i
EndStructure
Structure strGerber
vtable.i
Identification.q
BoardSize.Pos;in mm
DrawScaling.f
Unit.a;mm/inch
EndStructure
Procedure create()
Protected *this.strGerber=AllocateStructure(strGerber)
*this\vtable=?vtable
ProcedureReturn *this
EndProcedure
Procedure.q _GetIdentification(*this.strGerber)
ProcedureReturn *this\Identification
EndProcedure
Procedure _SetIdentification(*this.strGerber,value.q)
*this\Identification=value
EndProcedure
Procedure _GetBoardSizeX(*this.strGerber)
ProcedureReturn *this\BoardSize\X
EndProcedure
Procedure _SetBoardSizeX(*this.strGerber,value)
*this\BoardSize\X=value
EndProcedure
Procedure _GetBoardSizeY(*this.strGerber)
ProcedureReturn *this\BoardSize\Y
EndProcedure
Procedure _SetBoardSizeY(*this.strGerber,value)
*this\BoardSize\Y=value
EndProcedure
Procedure.a _GetUnit(*this.strGerber)
ProcedureReturn *this\Unit
EndProcedure
Procedure _SetUnit(*this.strGerber,value.a)
*this\Unit=value
EndProcedure
DataSection
vtable:
Data.i @_GetIdentification(),@_SetIdentification()
Data.i @_GetBoardSizeX(),@_SetBoardSizeX()
Data.i @_GetBoardSizeY(),@_SetBoardSizeY()
Data.i @_GetUnit(),@_SetUnit()
EndDataSection
EndModule
Re: Is it possible to restrict access on structure fields?
Posted: Fri Sep 08, 2023 5:51 am
by Rinzwind
Nope. With a few language additions structures could be a way better alternative for modules. As discussed multiple times before, but ignored by PB owner(s). Fully optional OOP-light idea.
Re: Is it possible to restrict access on structure fields?
Posted: Fri Sep 08, 2023 9:30 am
by benubi
I believe even in most OOP languages you have to go the way with GetVariable() methods to get the private variables of an "external" object. There's no private, public and friend classification of objects in PB which would be the way other languages handle access restrictions. I don't think that a structure in a OOP language will have elements defined as private or public, instead it's the entire structure pointer that would be public or private, but for objects (!) this will be different. In PB there's no object handling like that, the "objects" are structure pointers with a virtual table pointer as their first element.
Re: Is it possible to restrict access on structure fields?
Posted: Fri Sep 08, 2023 9:39 am
by NicTheQuick
You could do it like this maybe:
Code: Select all
Structure Gerber
Identification.q
BoardSize.Pos;in mm
Unit.a;mm/inch
EndStructure
Structure GerberInternal Extends Gerber
DrawScaling.f
EndStructure
The programmer using your module knows only about the Gerber structure but internally you simply use GerberInternal which has additional attributes.
Securely protecting the access to DrawScaling however will not be possible without creating a dedicated library or DLL/SO with its own memory management.
Re: Is it possible to restrict access on structure fields?
Posted: Fri Sep 08, 2023 12:42 pm
by Quin
The only language I've seen that puts access modifiers on struct fields is Rust, and that's partially because they basically treat structs like objects anyways (e.g. you can have methods on your struct). It would be really nice if PB could also adopt this, but I highly doubt it
Re: Is it possible to restrict access on structure fields?
Posted: Fri Sep 08, 2023 2:07 pm
by NicTheQuick
Quin wrote: Fri Sep 08, 2023 12:42 pm
The only language I've seen that puts access modifiers on struct fields is Rust, and that's partially because they basically treat structs like objects anyways (e.g. you can have methods on your struct). It would be really nice if PB could also adopt this, but I highly doubt it
There are other languages too: Java, C++. Even Python has that possibility but there it is more like a convention and the IDE would not allow you to access these fields, or you work with the @property decorator.
Re: Is it possible to restrict access on structure fields?
Posted: Fri Sep 08, 2023 2:40 pm
by jacdelad
Thanks to all with the answers. Extending the structure will leave the values accessible, though experimenting would be needed. I think I'll need an external object to do this.
XProfan is skso able to mark parts of a structure as private, that's why I asked. Since it can deploy precompiled units (=precompiled module) the private parts are kept truly private.
Re: Is it possible to restrict access on structure fields?
Posted: Tue Sep 12, 2023 12:49 pm
by Kulrom
In my opinion there is too much difficulty in hiding fields.
There are no hidden fields in classes in Python. And this doesn’t upset anyone. There is an agreement that hidden fields and methods begin with the character "_". For example "_field" or "_method". And the programmer does not use them. That's all.
If someone wants to shoot themselves in the foot, they will do it anyway.
If there is only one programmer, then this is not a problem at all. If the team is small, then you just need to discuss the rules.
Re: Is it possible to restrict access on structure fields?
Posted: Tue Sep 12, 2023 1:08 pm
by jacdelad
As long as PureBasic doesn't have any kind of precompiler which obfuscates the code I'll have to release it in full anyway. O worry more about someone accidently changing somethibg, than more about hiding something.