Testing if an object exists... explanation required

On Error Resume Next doesn't resolve the error that presents when the object doesn't exist. Check out Chip Pearson's blog on the subject <http://bit.ly/29MKyGd>.

You might want to replace On Error Resume Next with On Error Goto ResolveMissingObject (or some such tag). And of course include the tag and code to handle the error.

And could the reason the If Then code takes so long is that the document contains no element that matches the eleID in the doc.

Originally Posted by AB33

In OOPs, a reference variable-dDETAIL- either points to an object or not which is "NULL"- it does not point to an object.
In VBA, you have "Nothing" instead of "NULL".

Set dDETAIL = doc.getElementById(eleID)
I do not know the main reason for code not returning nothing if there is no object, but I suspect I do not think the set statement is meant to be clear-cut as either returning object or nothing. In VBA most things work or do not work through trial and error.
This line my prove my point.

If doc.getElementById(eleID) > 0 Then rng = doc.getElementById(eleID).outerText

Thanks for the reply AB33.
My understanding is:

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returns a count of the element that you're retrieving, doesn't it?
Given that it is searching for an element by ID , the count can only be 1 (if it exists) or zero (ie it does not exist). If you search by tagname then I assume you can get a return value of more than 1?

I included that bit of code because from what I understand it does actually test if an element exists. I think that it runs slower because it does the same thing twice, looks for the element to see if it exists , then looks for it again in order to get the outertext.

On my simplified example it would appear that it is more efficient using error trapping to test if an object exists?
Would that be a reasonable assumption to make?

Maybe you want:

If Len(doc.getElementById(eleID)) > 0 Then rng = doc.getElementById(eleID).outerText

Originally Posted by anrichards22

It is my understanding that you can NEVER have an object that is nothing simply because you can't set an object that is nothing.

I'm afraid your understanding is not correct. An object variable is either an object or it is Nothing. Often, when using an assignment, you do have to use an error handler and then test for Is Nothing.

It is not clear what you meant by this statement-

Using "On Error Resume Next" brings with it problems of its own

Would you care to elaborate?

I don't understand your example. This works fine:

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Originally Posted by anrichards22

However, if x is NOTHING then VBA throws an error when you try to set it rather than setting it as nothing.
Is there an explanation for this?

VBA does not throw an error when you try and set an object to Nothing. There are some methods that throw an error rather than simply returning Nothing when they fail, but that is not the same thing. Consider the Find method, which will happily return Nothing if the search value is not found.

In relation to On Error Resume Next:
I was merely suggesting that skipping over errors (on error resume next) leads to unpredictable results.

Indeed. That is why one should limit the scope of an On Error Resume Next statement to as small as possible- preferably just one line- before resetting error handling, via an On Error Goto 0 or other method.

What do you mean by "it" exactly? Some methods return Nothing, others will raise an error. It just depends on how they were programmed.

It is this part that raises an error

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not the variable or the Set statement. It is simply the way that the getElementbyID method was coded- presumably for internal consistency. Therefore you require the error handler

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note the red line to clear the effect of the OERN line.

Did you previously set doc?

What is the error message when eleId doesn't exist?

That is the error for this line

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?

That seems very strange indeed. I would only expect that error if the doc variable were Nothing.

Originally Posted by anrichards22

As I understand it now...different methods treat objects differently..

I am just curious as to why.

Specifically in relation to html objects...I have searched far and wide and almost always the advice given to test if a html element exists is

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It seems there is a third option: An error. In VBA find function, you get two options: either points to a object or nothing, but this consistency does not work in DOM objects. IMO, it is a waste of time to find out the reason for inconsistency.