Comments on: What do ByRef and ByVal mean to you? http://www.dailydoseofexcel.com/archives/2005/04/28/what-do-byref-and-byval-mean-to-you/ Daily posts of Excel tips…and other stuff Thu, 09 Feb 2012 23:42:03 +0000 hourly 1 http://wordpress.org/?v=3.2.1 By: Jim Thomlinson http://www.dailydoseofexcel.com/archives/2005/04/28/what-do-byref-and-byval-mean-to-you/#comment-39810 Jim Thomlinson Fri, 12 Jun 2009 17:14:00 +0000 http://www.dailydoseofexcel.com/?p=1108#comment-39810 <p>The fundamental difference between byref and byval is that by ref passes the variable into the function, where as byval makes a copy of the variable and passes that in. Knowing that question 1 is relatively obvious. Question 2 is a bit tougher. The issue is one of performance. Copying most variables is easy as the size is known, but a string is actually a null terminated array of characters so the copy requires more overhead. Question 3 is where it gets difficult because you need to understand that references to objects are handled by pointers and that the copy only copies the pointer and not the entire object. From that stand point I do not see any value to passing ByVal in #3. Let me know if I am off the mark here. Always good to learn.</p> <p>The only other question I would have asked is if you do not specify ByRef or ByVal then what is the default? Interesting how many people have no idea.</p> The fundamental difference between byref and byval is that by ref passes the variable into the function, where as byval makes a copy of the variable and passes that in. Knowing that question 1 is relatively obvious. Question 2 is a bit tougher. The issue is one of performance. Copying most variables is easy as the size is known, but a string is actually a null terminated array of characters so the copy requires more overhead. Question 3 is where it gets difficult because you need to understand that references to objects are handled by pointers and that the copy only copies the pointer and not the entire object. From that stand point I do not see any value to passing ByVal in #3. Let me know if I am off the mark here. Always good to learn.

The only other question I would have asked is if you do not specify ByRef or ByVal then what is the default? Interesting how many people have no idea.

]]> By: karthick http://www.dailydoseofexcel.com/archives/2005/04/28/what-do-byref-and-byval-mean-to-you/#comment-39776 karthick Thu, 11 Jun 2009 06:48:00 +0000 http://www.dailydoseofexcel.com/?p=1108#comment-39776 <p>Thanks a lot for your short and excellent functions. </p> <p>Appreciate your publishment...thanks once again</p> <p>:D</p> <p>thanks<br> Karthick</p> Thanks a lot for your short and excellent functions.

Appreciate your publishment…thanks once again

:D

thanks
Karthick

]]> By: ByRef and ByVal « Roy MacLean’s VBA Blog http://www.dailydoseofexcel.com/archives/2005/04/28/what-do-byref-and-byval-mean-to-you/#comment-39190 ByRef and ByVal « Roy MacLean’s VBA Blog Fri, 01 May 2009 13:23:00 +0000 http://www.dailydoseofexcel.com/?p=1108#comment-39190 <p>[...] 2009 VBA Code 0 Comments Tags: Software, VBA I recently came across a discussion about ByRef and ByVal, which I found a bit confusing. So I thought I'd summarise my (possibly mis-) understanding [...]</p> [...] 2009 VBA Code 0 Comments Tags: Software, VBA I recently came across a discussion about ByRef and ByVal, which I found a bit confusing. So I thought I’d summarise my (possibly mis-) understanding [...]

]]> By: greg http://www.dailydoseofexcel.com/archives/2005/04/28/what-do-byref-and-byval-mean-to-you/#comment-23905 greg Sat, 05 May 2007 01:47:00 +0000 http://www.dailydoseofexcel.com/?p=1108#comment-23905 <p>I can tell there is more book smart than real life preactice in come of these responses. A Value passed BYREF will chage the vlaue in the calling method, as most of us know. What I have not seen anyone pick up on is the 1001 uses for passing values byref in a function. How about the good old introduction to VB.NET book. Most of realize that there are often times an integer of 0 may be returned back from a function without it being in error. By (for example) returning a true or false back from the method or function we can say that the argument we passed into our parameter was infact successfuly processed. Of course this is just one simplistic example.</p> I can tell there is more book smart than real life preactice in come of these responses. A Value passed BYREF will chage the vlaue in the calling method, as most of us know. What I have not seen anyone pick up on is the 1001 uses for passing values byref in a function. How about the good old introduction to VB.NET book. Most of realize that there are often times an integer of 0 may be returned back from a function without it being in error. By (for example) returning a true or false back from the method or function we can say that the argument we passed into our parameter was infact successfuly processed. Of course this is just one simplistic example.

]]> By: Jamie Collins http://www.dailydoseofexcel.com/archives/2005/04/28/what-do-byref-and-byval-mean-to-you/#comment-12092 Jamie Collins Tue, 03 May 2005 08:57:00 +0000 http://www.dailydoseofexcel.com/?p=1108#comment-12092 <p>In response to #14:</p> <p>I think you *do* need to explain because I can see nothing in the article which creates a copy of an object instance. It would be a very handy thing to create a copy instance (rather than a copy pointer to the same instance) but I've always considered it out of reach because of the fact a single COM object can be stored in multiple memory locations and hence have different references for each (think mulitple interfaces).<br> Jamie.</p> <p>–</p> In response to #14:

I think you *do* need to explain because I can see nothing in the article which creates a copy of an object instance. It would be a very handy thing to create a copy instance (rather than a copy pointer to the same instance) but I’ve always considered it out of reach because of the fact a single COM object can be stored in multiple memory locations and hence have different references for each (think mulitple interfaces).
Jamie.

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]]> By: Jamie Collins http://www.dailydoseofexcel.com/archives/2005/04/28/what-do-byref-and-byval-mean-to-you/#comment-12091 Jamie Collins Tue, 03 May 2005 08:31:00 +0000 http://www.dailydoseofexcel.com/?p=1108#comment-12091 <p>Joseph: "Are we looking at issues that have real life meaning here, or are we navel gazing?"</p> <p>Good question. Remember the context is a job interview. </p> <p>I'd expect everyone to know the answer to scenario a. If they gave me the answer I was looking after for scenario b then I'd know they would have an appreciating of performance issues. If they gave a sensible answer for scenario b then they'd have justified putting 'COM' or 'ActiveX' on their cv/resume. </p> <p>If they were confused by the latter two scenarios then the chances are they haven't much experience of component based or object oriented programming in VBA. Mentioning the concept of 'trusted code' or the implications of marshalling (I didn't say the Function was in-process) would earn bonus points.</p> <p>You may find it interesting that the best answer I got to scenario b went something like, ' I think the answer is [incorrect assumption here] but I'm really not sure. You've got me interested though. What is the correct answer?' This candidate starts Monday. How real life is that?</p> <p>Jamie.</p> <p>–</p> Joseph: “Are we looking at issues that have real life meaning here, or are we navel gazing?”

Good question. Remember the context is a job interview.

I’d expect everyone to know the answer to scenario a. If they gave me the answer I was looking after for scenario b then I’d know they would have an appreciating of performance issues. If they gave a sensible answer for scenario b then they’d have justified putting ‘COM’ or ‘ActiveX’ on their cv/resume.

If they were confused by the latter two scenarios then the chances are they haven’t much experience of component based or object oriented programming in VBA. Mentioning the concept of ‘trusted code’ or the implications of marshalling (I didn’t say the Function was in-process) would earn bonus points.

You may find it interesting that the best answer I got to scenario b went something like, ‘ I think the answer is [incorrect assumption here] but I’m really not sure. You’ve got me interested though. What is the correct answer?’ This candidate starts Monday. How real life is that?

Jamie.

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]]> By: Joseph http://www.dailydoseofexcel.com/archives/2005/04/28/what-do-byref-and-byval-mean-to-you/#comment-11725 Joseph Fri, 29 Apr 2005 18:11:00 +0000 http://www.dailydoseofexcel.com/?p=1108#comment-11725 <p>I'd like to know what practical impact the answers to these questions have.</p> <p>Are we looking at issues that have real life meaning here, or are we navel gazing?</p> I’d like to know what practical impact the answers to these questions have.

Are we looking at issues that have real life meaning here, or are we navel gazing?

]]> By: Billkamm http://www.dailydoseofexcel.com/archives/2005/04/28/what-do-byref-and-byval-mean-to-you/#comment-11717 Billkamm Fri, 29 Apr 2005 15:24:00 +0000 http://www.dailydoseofexcel.com/?p=1108#comment-11717 <p>In response to #11:</p> <p>This article can probably explain it better than I could:</p> <p><a href="http://www.windowsdevcenter.com/pub/a/oreilly/windows/ron/objects.html?page=last" rel="nofollow">http://www.windowsdevcenter.com/pub/a/oreilly/windows/ron/objects.html?page=last</a></p> In response to #11:

This article can probably explain it better than I could:

http://www.windowsdevcenter.com/pub/a/oreilly/windows/ron/objects.html?page=last

]]> By: jkpieterse http://www.dailydoseofexcel.com/archives/2005/04/28/what-do-byref-and-byval-mean-to-you/#comment-11713 jkpieterse Fri, 29 Apr 2005 12:45:00 +0000 http://www.dailydoseofexcel.com/?p=1108#comment-11713 <p>I guess when the function needs to alter the content of more than just one (object) variable, ByRef comes in handy. </p> <p>If e.g. the function is set up to be a boolean function that denotes whether any errors have occurred inside the function, one needs to use byref arguments to get at the actual results of the function.</p> I guess when the function needs to alter the content of more than just one (object) variable, ByRef comes in handy.

If e.g. the function is set up to be a boolean function that denotes whether any errors have occurred inside the function, one needs to use byref arguments to get at the actual results of the function.

]]> By: Jon Peltier http://www.dailydoseofexcel.com/archives/2005/04/28/what-do-byref-and-byval-mean-to-you/#comment-11712 Jon Peltier Fri, 29 Apr 2005 12:12:00 +0000 http://www.dailydoseofexcel.com/?p=1108#comment-11712 <p>"I said that the Function makes no change to the variable's value "</p> <p>Oh, you meant the function by design makes no change. I thought you implied the function changed it but somehow the change wasn't reflected in the passed variable's value.</p> <p>Duh.</p> “I said that the Function makes no change to the variable’s value “

Oh, you meant the function by design makes no change. I thought you implied the function changed it but somehow the change wasn’t reflected in the passed variable’s value.

Duh.

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