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UDF Parameter Question

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    #1

    UDF Parameter Question

    Hi All,

    I was just curious what the prevailing thought might be on the following when creating / using UDF's. If you have a global variable previously defined as say gvMyRefNum and it is populated with a value. Is there any difference one way or the other (better code isolation. stability, etc.) if you either pass or don't pass the global variable as a parameter to the UDF?

    For example:

    RunMyCode(gvMyRefNum)

    versus

    RunMyCode() <-and gvMyRefNum is just referenced inside the UDF


    Obviously, both ways work......just curious if there is a prevailing thought on best practice in this situation?


    Regards,

    Jeff
    Tags: None
    #2
    Re: UDF Parameter Question

    Jeff,
    I can see where context can play a big part in this....many times I will have a variable dimensioned from a form that will later be used in a UDF.....other times, if its value can be set from within the function, then I dimension and set it there. Where a variable will be used and if the variable will be used multiple times determines much.
    Mike
    __________________________________________
    It is only when we forget all our learning that we begin to know.
    It's not what you look at that matters, it's what you see.
    Henry David Thoreau
    __________________________________________



    Comment

      #3
      Re: UDF Parameter Question

      ...many times I will have a variable dimensioned from a form that will later be used in a UDF.....other times, if its value can be set from within the function, then I dimension and set it there.
      Yep, that is what I do as well Mike.

      I just was wondering if there was any "under the hood" stuff that made one way better / more bulletproof than another?

      Ira...you out there? :):)

      Comment

        #4
        Re: UDF Parameter Question

        I would be interested as well in other's thoughts in case I am missing something or a way to better my code.

        One thing I always make sure of in functions is that if something can be dimensioned local I do that as then I am assured that when using the same function sometimes many times in a row, that the variables will not be stepping on each other.

        Regarding a global, once dimmed, it is there regardless until the database is closed....so whether it is dimmed on startup or when first used, it makes little difference IMO.
        Mike
        __________________________________________
        It is only when we forget all our learning that we begin to know.
        It's not what you look at that matters, it's what you see.
        Henry David Thoreau
        __________________________________________



        Comment

          #5
          Re: UDF Parameter Question

          Jeff,

          Always choose the smallest scope for your variables to get your app working and always pass variables by reference or value at a function. Don't use globals, thats a lazy habit. :)
          Marcel

          I hear and I forget. I see and I remember. I do and I understand.
          ---- Confusius ----

          Comment

            #6
            Re: UDF Parameter Question

            Originally posted by Marcel Kollenaar View Post
            Jeff,

            Always choose the smallest scope for your variables to get your app working and always pass variables by reference or value at a function. Don't use globals, thats a lazy habit. :)

            Hi Marcel,

            Thanks for your reply.

            Yes...that is what I do (choose smallest scope). In the instances where I need a global, I was just curious whether it was more "bulletproof" to pass the variable as a parameter (verus just using the global variable inside the UDF) and if anyone knew why that might be the case?

            The root of this question is that I had seen a few "bizarre" happenings in this area (i.e. the resultant action of the code in the UDF did not perform the intended action based on the "known" variable value). I changed a few UDF's to handle a parameter instead of just using a variable that existed. The variables were not global in some of these instances....but the UDF still used them (but not by being passed as a parameter). The weird behavior was very sporadic....by that I mean....I knew what the output of the UDF should have been based on the variable value....but it did not always work out that way. Once, I changed
            the UDF to take the same value(variable) as a parameter....things have seemed more reliable.

            I guess I just answered my own question! :) I don't fully understand why that has occured.....but I will be creating/changing all my UDF's to take these variables as parameters.

            Regards,

            Jeff

            Comment

              #7
              Re: UDF Parameter Question

              Jeff,

              During a A5 session all variables are trown in a big memory pool. Variables are "deleted" by the default behaviour of specific parts such as forms. After a form closes the variables local to the form are gone. But if somewhere in your program a variable is created by some code and given a value and not deleted it can become a hazardous item when in other parts a variable is used with the same name and not explicit dimensioned.
              Marcel

              I hear and I forget. I see and I remember. I do and I understand.
              ---- Confusius ----

              Comment

                #8
                Re: UDF Parameter Question

                Hi Marcel,

                Thanks....yeah...I fully understand how variables work in Alpha. I guess my example to start this thread was poor.

                My question really has nothing to do with variables. It is with UDF's and Parameters. Here is another example that more clearly defines what I was looking for. In any case, I have adopted the strategy to always pass my reference values as parameters now. I still would like to know what the "under the hood" differences (if any) exist between the code below. When running a UDF from a form, I have seen instances where Alpha did not ALWAYS evaluate the value correctly with the second example below....but if the value is passed as a parameter it did evaluate correctly.

                RunMyCode(parentform:myfieldname.value)

                versus

                RunMyCode() <-and parentform:myfieldname.value is just referenced inside the UDF


                Regards,

                Jeff

                Comment

                  #9
                  Re: UDF Parameter Question

                  Jeff,
                  Much more clear....I have always passed such arguments directly into the function as, like you, have found that the UDF cannot always "see" the form or its values.
                  Mike
                  __________________________________________
                  It is only when we forget all our learning that we begin to know.
                  It's not what you look at that matters, it's what you see.
                  Henry David Thoreau
                  __________________________________________



                  Comment

                    #10
                    Re: UDF Parameter Question

                    Clear, agree with Mike.
                    Marcel

                    I hear and I forget. I see and I remember. I do and I understand.
                    ---- Confusius ----

                    Comment

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