[AccessD] Pseudo Pointer to a Function

Shamil,

    Thanks for confirming. So nice of you. 

     William's post of 23-Jun-2009 gave the impression that he had been successful in using CallByName() function even for calling subs / functions located in standard / general modules. Apparently, that is not the case and there has been no confirmatory corroboration from him.

    With your clarification, the thread attains proper completion.

    In conclusion, for calling a sub or function using a string variable holding the name of the sub or function, the following considerations appear to apply:

    1 - CallByName() function is meant (and is the preferred method) for calling public subs / functions belonging to form or class modules. (Subs / functions located in standard / general modules can not be called by this method). Typical syntax:

    (a) Called proc is in the same form:
    CallByName Me, "<<CalledProcName>>", VbMethod

    (b) Called proc is in another form:
    CallByName Forms("<<TargetFormName>>"),  _
                      "<<CalledProcName>>", VbMethod

    (c) Called proc is in a class:
    CallByName PointerToClassObject,  _
                      "<<CalledProcName>>", VbMethod

    2 - For calling public subs / functions located in standard / general modules, Application.Run command or Eval() function can be used.

    Note: For all the methods mentioned in 1 & 2 above, the called entity has to be public.

    3 - If Eval() function is used, the called entity has to be a function (with or without return value). Otherwise error. Typical syntax:  Eval(strCall) - where variable strCall holds the complete string depicting name of function as well as its arguments, e.g.:
    strCall = "MyFunction('ABC')"    ' Here, 'ABC' is the argument.
    Debug.Print Eval(strCall)

    4 - Application.Run command can handle subs as well as functions (if return value is not material). This command is not suited for calling subs / functions in form modules. Here, the first argument is just the name of procedure, followed by optional other arguments representing arguments meant for the procedure or function.

    5 - As an academic interest, Eval() function can be used to call a public function in form modules also, if no argument is required to be passed. For example
    strCall = "Forms('<<TargetFormName>>').MyFunction"
    Debug.Print Eval(strCall)
    
    Note: The function parenthesis are not to be used, i.e. not MyFunction(). Moreover, the target function gets activated twice. Therefore better use CallByName() function.
    
Best wishes,
A.D. Tejpal
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  ----- Original Message ----- 
  From: Shamil Salakhetdinov 
  To: 'Access Developers discussion and problem solving' 
  Sent: Wednesday, July 01, 2009 20:15
  Subject: Re: [AccessD] Pseudo Pointer to a Function


  Hi A.D.,

  I suppose CallByName will not work for standard/general modules'
  subs/functions as CallByName is based (I guess) on COM IDispatch interface's
  Invoke(...) method (http://en.wikipedia.org/wiki/IDispatch) and IDispatch
  interface is implemented in MS Access/VBA only for custom classes' modules,
  which are instantiated internally as COM objects.
  --
  Shamil

  -----Original Message-----
  From: accessd-bounces at databaseadvisors.com
  [mailto:accessd-bounces at databaseadvisors.com] On Behalf Of A.D.Tejpal
  Sent: Wednesday, July 01, 2009 5:55 PM
  To: Access Developers discussion and problem solving
  Subject: Re: [AccessD] Pseudo Pointer to a Function

      This refers to my post of 27-Jun-2009, placed below. While response from
  William is awaited, it would be nice if other members of this forum could
  also kindly conduct a test and confirm whether any success with using
  CallByName() function where the called procedure / function is in a general
  module.

  Best wishes,
  A.D. Tejpal
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