Passing nil to ByRef

General
1

Passing nil to a byref deceleration in the method parameters seems to not be allowed. What’s the best alternative to this?
Should I create an instance of an object of the type of the object being passed in or is there a better approach which someone could recommend.

Here is an example of a method:

dim myObj as MsgBoxShower
myMethod(myObj)
myObj.ShowMsgBox("hello")

In the above code, I would intend to use byref to manipulate the myObj value but this is invalid?

Thanks

2

show the signature of the “myMethod”

sub myMethod(byref xyz AS MsgBoxShower)

should work… although depending on what MsgBoxShower is subclassed from, objects are always passed byRef

3

[quote=219196:@Dave S]show the signature of the “myMethod”

sub myMethod(byref xyz AS MsgBoxShower)

should work… although depending on what MsgBoxShower is subclassed from, objects are always passed byRef[/quote]
When calling myMethod, I get a NilObjectException?

Thanks

4

The exception is probably coming from within myMethod. Like it’s working on the parameter without checking it for nil. Otherwise passing in nil is fine.

5

Within myMethod it just does ‘myObj = new MsgBoxShower’. I got my method I wrote to exclusively set the variable to a new instance.

Thanks

6

Hmm, I don’t know, that should work. Here’s the code I used to confirm what I think I know and I get the msgbox.

[code]Sub Action()
dim d As Date
myMethod(d)
MsgBox d.LongDate
End Sub

Private Sub myMethod(byref d As Date)
d = new Date
End Sub
[/code]

Maybe there’s something in the MsgBoxShower Constructor that’s exceptioning. Try breaking before calling myMethod and step through until you get the NOE. What line is that?

7

[quote=219205:@Will Shank]Hmm, I don’t know, that should work. Here’s the code I used to confirm what I think I know and I get the msgbox.

[code]Sub Action()
dim d As Date
myMethod(d)
MsgBox d.LongDate
End Sub

Private Sub myMethod(byref d As Date)
d = new Date
End Sub
[/code]

Maybe there’s something in the MsgBoxShower Constructor that’s exceptioning. Try breaking before calling myMethod and step through until you get the NOE. What line is that?[/quote]
The ‘myMethod(d)’ line is highlighted with a NilObjectException.

8

Within myMethod, do you ever create a new object that ultimately gets assigned back to myObj?

9

what is the CONSTRUCTOR for MsgBoxShower? perhaps therein lies your culprit

10

Very weird, I can’t even imagine what could cause a NOE on that line.

11

I found the problem still occurs if I assign the value to a new instance before executing the method. The Constructor does not have any kind of conflict. Kem, the method’s whole point is to assign a new value to that variable. Thanks

12

Time to post your code, I think.

14

My code

In Window1. open

Sub Open()
  dim myObj as MsgBoxShower
  myMethod(myObj)
  myObj.ShowMsgBox("hello")
End Sub

myMethod on Window1 is

Private Sub myMethod(byref f as MsgBoxSHower)
  f = new MsgBoxSHower
  
  if f is nil then
   break // note it doesn't break here
  end if
End Sub

plus I have a class called msgboxshower with one method

Sub ShowMsgBox(msg as string)
  MsgBox msg
End Sub

and this shows up a msgbox that says hello
so something else is going ion in your code

15

Are you using Operator_Convert? That could cause a NOE on that line or when assigning, depending on your converts and types.

16

Your original code is this:

dim myObj as MsgBoxShower myMethod(myObj) myObj.ShowMsgBox("hello")
It should be this:

dim myObj as new MsgBoxShower myMethod(myObj) myObj.ShowMsgBox("hello")

17

that has the effect of creating one just to throw it away like

dim d as new date 
d =  fodleritem.CreationDate

does
And if you look at the code I posted completely unnecessary
It works with a nil reference passed
No idea why olivers code isn’t working but the snippets he’s posted are too short to determine why

18

I overlooked that I called the method from a variable. That’s where the problem sits. Thanks