simple question on parameter passing

[Geoff]

Consider the procedure



Private Sub Adder(ByVal Num1 As Integer, etc. )



End Sub



which called by Call Adder( TxtNum1,.) where TxtNum1 is a text box.





Why does Num1 accept the value as an integer when the actual parameter being
passed is of type string? Why no type mismatch error??



Many thanks

Geoff

[Karl E. Peterson]

Re: simple question on parameter passing

Geoff wrote:

Consider the procedure
>
Private Sub Adder(ByVal Num1 As Integer, etc. )
>
End Sub
>
which called by Call Adder( TxtNum1,.) where TxtNum1 is a text
box.
>
Why does Num1 accept the value as an integer when the actual
parameter being passed is of type string? Why no type mismatch
error??

That's one of the "features" introduced at VB4, and commonly referred to as
"Evil Type Coercion". If VB can coerce, it does. Here's an article I wrote
on that, way back when:

Coercion Aversion

http://vb.mvps.org/articles/pt199511.pdf

--

[Steve Gerrard]

Re: simple question on parameter passing


"Karl E. Peterson" <karl@mvps.orgw rote in message
news:edpo6h$tfd $1@emma.aioe.or g...

Geoff wrote:

>Consider the procedure
>>
>Private Sub Adder(ByVal Num1 As Integer, etc. )
>>
>End Sub
>>
>which called by Call Adder( TxtNum1,.) where TxtNum1 is a text
>box.
>>
>Why does Num1 accept the value as an integer when the actual
>parameter being passed is of type string? Why no type mismatch
>error??

>
That's one of the "features" introduced at VB4, and commonly referred to as
"Evil Type Coercion". If VB can coerce, it does. Here's an article I wrote
on that, way back when:
>
Coercion Aversion

http://vb.mvps.org/articles/pt199511.pdf

>

IN fact, when you pass TxtNum1, you are passing a TextBox, not a string. VB also
finds the default property of the TextBox, which is Text, which is a string, and
then does ETC and passes the result. Since default properties can also get you
in trouble, it is usually considered better to use TxtNum1.Text directly:
If IsNumeric(TxtNu m1.Text) Then
Call Adder(CInt(TxtN um1.Text))
End If