OOP: Programmatical finding all objects for __QUERYINTERFACE

2020-02-27T14:12:52.297000Z

Originally created by: scott_cunningham

Sorry, the project code is not allowed to be shared. Here is finally how I used the __QUERYINTERFACE to add a qualified object (only showing collection specific info):

FUNCTION_BLOCK FINAL ClassFaultObjectsCollection
VAR
   Collection   : ARRAY[1..GVL_COLLECT.MAX_OBJECTS] OF IFault;
   ObjNames   : ARRAY[1..GVL_COLLECT.MAX_OBJECTS] OF STRING;
   _ArrayOver   : BOOL;
   _BadObj      : INT;
   _DupeObj   : INT;
   _OverObj   : INT;
   _TotalObj   : INT;
END_VAR
(* Add object to the collection.
-----------------------------------------------------------------------
Call this method to add an object to the collection array:
   AddObject(THIS^)
Found below is typical code required.  'Obj' must be converted from an
IAll type to the interface type specific to the collection you are
implementing
*)
METHOD FINAL AddObject
VAR_INPUT
   (* object*)
   Obj   : IAll;
END_VAR
VAR
   Cast: IFault;
   J   : INT;
END_VAR
IF (__QUERYINTERFACE(Obj, Cast)) THEN
   // make sure haven't already added this object
   FOR J:= 1 TO _TotalObj DO
      IF Collection[J] = Cast THEN
         // object pointer matches - dupe!
         _DupeObj:= _DupeObj + 1;
         RETURN;
      END_IF
   END_FOR
   
   IF _TotalObj < GVL_COLLECT.MAX_OBJECTS THEN
      _TotalObj:= _TotalObj + 1;
      Collection[_TotalObj]:= Cast;
      ObjNames[_TotalObj]:= Obj.Instance;
   ELSE
      _ArrayOver:= TRUE;
      _OverObj:= _OverObj + 1;
   END_IF
   
ELSE
   _BadObj:= _BadObj + 1;
END_IF

So if you have a FB that should be added to the collection, it can do it in the FB_INIT of itself (but it must implement the matching interface - or it's a bad object...):

FUNCTION_BLOCK WantToFault IMPLEMENTS IFault
...
some code
...
METHOD FB_init : bool
VAR_INPUT
   bInitRetains : BOOL; // Initialization of the retain variables
   bInCopyCode : BOOL;  // Instance moved into copy code
   FaultCollector : REFERENCE TO ClassFaultObjectsCollection;
END_VAR
FaultCollector.AddObject(THIS^);
END_FUNCTION_BLOCK

On instantiation, the instance of WantToFault will call the collector's AddObject() method and pass itself to it. The collector will verify it should be an IFault member, and add's it, if necessary.

OOP: Programmatical finding all objects for __QUERYINTERFACE

2020-02-27T14:12:51.954000Z

@Scott,
Would you be kind enough and post us an archived project?

Thanks in advance!

OOP: Programmatical finding all objects for __QUERYINTERFACE

2020-02-27T14:12:50.883000Z

I have an ObjectPool too, You can add {attribute 'global_init_slot' := '49995'} at program or GVL init, it ensures that the intialization of the element which has this attribute will be instantiated before all others (The default init slot is 50000).

OOP: Programmatical finding all objects for __QUERYINTERFACE

2020-02-27T14:12:50.537000Z

Thanks Scott, I do have one more question because I noticed something strange.

If I declare the InterfaceHandler in one GVL and Drive1in another GVL, it doesn't work.
The program runs but it's like the InterfaceHandler code never executes.

If they are put in the same GVL, it works.
It also works if Drive1 is declared in a POU (as in your example code).

I can only assume that this has something to do with the order that Codesys creates the variables and/or initialises them internally.
Do you have any insight to this matter?

OOP: Programmatical finding all objects for __QUERYINTERFACE

2020-02-27T14:12:50.123000Z

Originally created by: scott_cunningham

Online change has not been a problem when changing the logic. Adding or removing objects is a different story. I never use online change when I add or remove variables/objects.

OOP: Programmatical finding all objects for __QUERYINTERFACE

2020-02-27T14:12:49.090000Z

Scott, it's been some years but I would like to know how you handle online changes.
As I understand it, FB_init only executes after a cold reset.
Doesn't this mean your arrays can be corrupted by online changes? If so, could you make use of fb_exit and fb_reinit somehow?

OOP: Programmatical finding all objects for __QUERYINTERFACE

2020-02-27T14:12:48.550000Z

Originally created by: scott_cunningham

Posting solution for those who can use it. Solution requires usage of FB_init() for each Class type. In this way, the arrays of objects are already filled at program start:

...define some interfaces...

INTERFACE IAllObjects// absolute base class
   METHOD Fb_init : BOOL
   VAR_INPUT
      bInitRetains : BOOL; // Initialization of the retain variables
      bInCopyCode : BOOL; // Instance moved into copy code
   END_VAR

INTERFACE IConveyor EXTENDS IAllObjects // interface for conveyors

INTERFACE IDrive EXTENDS IAllObjects // interface for drives

...define global collection arrays...

GVL_OBJECTS
   VAR_GLOBAL CONSTANT
      MAX_OBJECTS: INT:= 10;
   END_VAR
   VAR_GLOBAL
      CollectionAllObjects: CollectionHandlerAll; // maintains array of all objects
      CollectionDrives: CollectionHandlerDrives; // maintains array of drives
      CollectionConveyors: CollectionHandlerConveyors; // maintains array of conveyors
   END_VAR

...define FB to handle array collections...

FUNCTION_BLOCK CollectionHandlerAll
VAR_INPUT
END_VAR
VAR_OUTPUT
   TotalObjects: INT; // total objects found - use for FOR/NEXT loop iterations of methods
END_VAR
VAR
   Collection: ARRAY[1..GVL_OBJECTS.MAX_OBJECTS] OF IAllObjects; // object array
END_VAR
   METHOD AddObject
   VAR_INPUT
      Obj   : IAllObjects;
   END_VAR
   TotalObjects:= TotalObjects + 1;
   Collection[TotalObjects]:= Obj;

FUNCTION_BLOCK CollectionHandlerConveyor
VAR_INPUT
END_VAR
VAR_OUTPUT
   TotalObjects: INT; // total objects found - use for FOR/NEXT loop iterations of methods
END_VAR
VAR
   Collection: ARRAY[1..GVL_OBJECTS.MAX_OBJECTS] OF IConveyor; // object array
END_VAR
   METHOD AddObject
   VAR_INPUT
      Obj   : IConveyor;
   END_VAR
   TotalObjects:= TotalObjects + 1;
   Collection[TotalObjects]:= Obj;

FUNCTION_BLOCK CollectionHandlerDrive
VAR_INPUT
END_VAR
VAR_OUTPUT
   TotalObjects: INT; // total objects found - use for FOR/NEXT loop iterations of methods
END_VAR
VAR
   Collection: ARRAY[1..GVL_OBJECTS.MAX_OBJECTS] OF IDrive; // object array
END_VAR
   METHOD AddObject
   VAR_INPUT
      Obj   : IDrive;
   END_VAR
   TotalObjects:= TotalObjects + 1;
   Collection[TotalObjects]:= Obj;

...define device FBs...

FUNCTION_BLOCK ClassConveyor IMPLEMENTS IConveyor // conveyor FB
VAR_INPUT
END_VAR
VAR_OUTPUT
END_VAR
VAR
END_VAR
   METHOD Fb_init : BOOL
   VAR_INPUT
      bInitRetains : BOOL; // Initialization of the retain variables
      bInCopyCode : BOOL; // Instance moved into copy code
   END_VAR
   GVL_OBJECTS.CollectionAllObjects.AddObject(THIS^);   // add instance to all objects collection
   GVL_OBJECTS.CollectionConveyors.AddObject(THIS^);   // add instance to conveyor collection

FUNCTION_BLOCK ClassDrive IMPLEMENTS IDrive // drive FB
VAR_INPUT
END_VAR
VAR_OUTPUT
END_VAR
VAR
END_VAR
   METHOD Fb_init : BOOL
   VAR_INPUT
      bInitRetains : BOOL; // Initialization of the retain variables
      bInCopyCode : BOOL; // Instance moved into copy code
   END_VAR
   GVL_OBJECTS.CollectionAllObjects.AddObject(THIS^);   // add instance to all objects collection
   GVL_OBJECTS.CollectionDrives.AddObject(THIS^);      // add instance to drives collection

...now main program...

PROGRAM PLC_PRG
VAR
   Drive1, Drive2: ClassDrive;
   Conv1, Conv2: ClassConveyor;
END_VAR

On program start, arrays for all objects, conveyors and drives are automatically built. You must manually code into the ClassXXX.FB_init() which collection arrays you want to have the object, but this is logical. Now it is easy to handle collection method calls as needed. If each drive has a Home() method, a simple FOR loop through the drives collection will call all drives. If all objects have a Reset() method, then a FOR loop through the all objects collection will call all objects. If I add another Conveyor (Conv3) or drive (Drive3) - no change is necessary - automatic object inclusion at project start. All without the slow __QUERYINTERFACE() call during runtime (penalty is RAM usage for holding arrays).

OOP: Programmatical finding all objects for __QUERYINTERFACE

2020-02-27T14:12:48.162000Z

Originally created by: scott_cunningham

If I put all of the objects into one large array, then it is quite easy to progmatically generate the smaller, specific arrays for each interface (some objects will belong to multiple interfaces due to their functionality):

//... main object array already populated....
//... now build array for IDrive objects....
// learn drive objects
ObjIndex:= 0;
FOR J:= 0 TO MAX_OBJ DO
   IF __QUERYINTERFACE(AllObjects[J], IDriveClass) THEN
      DriveObjects[ObjIndex]:= IDriveClass;
      ObjIndex:= ObjIndex + 1;
   END_IF
END_FOR
TotalDriveObjects:= ObjIndex;
//... now build array for IPinch objects....
ObjIndex:= 0;
FOR J:= 0 TO MAX_OBJ DO
   IF __QUERYINTERFACE(AllObjects[J], IPinchClass) THEN
      PinchObjects[ObjIndex]:= IPinchClass;
      ObjIndex:= ObjIndex + 1;
   END_IF
END_FOR
TotalPinchObjects:= ObjIndex;
//... now build array for Ixxxx objects....
//... etc

This, of course, takes some time, but no problem at machine power on. Just trying to avoid manually building the main array - but so far, it looks like I will have too!

OOP: Programmatical finding all objects for __QUERYINTERFACE

2020-02-27T14:12:47.161000Z

scott_cunningham hat geschrieben:
There is also the possibility that there will be some methods/properties that all objects may have to implement.

In this case I understand the generic interface, but I do not know a good solution for your problem.

The only thing I could imagine is to have a range inside the array for each specific type, e.g. 1-10 are drives, 11-20 the next type,....

OOP: Programmatical finding all objects for __QUERYINTERFACE

2020-02-27T14:12:46.816000Z

Originally created by: scott_cunningham

There will be quite a number of interfaces - at least 20 (I left all of these out of my sample code) and a large number of objects (many hundreds). To avoid using __QUERYINTERFACE during the actual machine operation (too slow doing this with nearly 1000 objects - results in about 2mS of execution time), I must build ahead of time, specific lookup arrays for each interface. Therefore, I create one single large array of all objects, and then build individual arrays from there (FOR loops for each interface compare against the whole list).

Additionally, by having IAllObjClass extend __System.IQueryInterface and requiring all objects to extend IAllObjClass, __QUERYINTERFACE is working.

There is also the possibility that there will be some methods/properties that all objects may have to implement.

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