Solved

no compile error while type mismatch

Posted on 2001-06-18
10
206 Views
Last Modified: 2010-05-02
i have a function:

MyFunction (Param1 as MyEnum) as Variant

While i call the function like this:
lsReturn = MyFunction("123")

MyEnum is a long and "123" is a literal string.

How come no compile error is prompt while compile and making a EXE?

0
Comment
Question by:chnelson
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
  • 4
  • 4
  • 2
10 Comments
 
LVL 9

Expert Comment

by:Valliappan AN
ID: 6201723
It is by design in MS way. Look at this link:

http://msdn.microsoft.com/library/devprods/vs6/vbasic/vbcon98/vbconpassingargumentstoprocedures.htm

There is a similar example, as you your case.

Cheers.
0
 
LVL 15

Expert Comment

by:ameba
ID: 6201742
Note that you are passing parameter "123" ByVal.
You are not passing string variable, but calculated value.

Option Explicit
Private Enum MyEnum
    dsNoRecords = 123
    dsNothingSelected
    dsNormal
    dsModify
    dsAdd
End Enum

Private Sub Form_Click()
    Dim lsReturn As Variant, x As String
    x = "123"
    lsReturn = MyFunction(x)     ' type mismatch error
   
    lsReturn = MyFunction((x))   ' no error, you are passing value of x
   
    lsReturn = MyFunction(x * 1) ' no error, you are passing calculated value
   
End Sub

Private Function MyFunction(Param1 As MyEnum) As Variant
    Beep
End Function
0
 
LVL 15

Expert Comment

by:ameba
ID: 6202582
If you pass parameter by value, VB compiler will insert converson function automatically.
0
Salesforce Has Never Been Easier

Improve and reinforce salesforce training & adoption using WalkMe's digital adoption platform. Start saving on costly employee training by creating fast intuitive Walk-Thrus for Salesforce. Claim your Free Account Now

 
LVL 9

Expert Comment

by:Valliappan AN
ID: 6203081
A nice explanation by ameba. :)
0
 
LVL 1

Author Comment

by:chnelson
ID: 6203158
ameba,

is it some way to disable that kind of auto convertion?

This kind of weak type checking is really dangerous which cause lots of run-time error before delopying the EXE to customers.
0
 
LVL 1

Author Comment

by:chnelson
ID: 6203163
ameba,

is it some way to disable that kind of auto convertion?

This kind of weak type checking is really dangerous which cause lots of run-time error before delopying the EXE to customers.
0
 
LVL 15

Accepted Solution

by:
ameba earned 10 total points
ID: 6203321
>is it some way to disable that kind of auto convertion?

Type checking is present if you pass variable ByRef.

VB will do many things 'behind the scene' to allow easy and fast programming.  If you remove 'Option Explicit' you don't have to declare variables.

Of course this can be dangerous, many VB programmers asked for 'Option Strict' or 'Option Anal Strict' to disable those 'features'...
0
 
LVL 1

Author Comment

by:chnelson
ID: 6206583
oh...
i got it...
asking you for a comment ameba,
to enforce strong type checking,
is it a good way to use ByRef instead of ByVal?
the only side-effect i think is that the parameters (ByRef) may be modified accidentally...
0
 
LVL 15

Expert Comment

by:ameba
ID: 6206660
>to enforce strong type checking,
>is it a good way to use ByRef instead of ByVal?

No, use ByVal if you need to pass parameter one-way [in]
use ByRef if you need to pass parameter two-way [in]+[out]

--
Please, maintain your old questions! You still have many opened questions.
0
 
LVL 1

Author Comment

by:chnelson
ID: 6207087
thanks ameba, very clear explaination
0

Featured Post

Industry Leaders: We Want Your Opinion!

We value your feedback.

Take our survey and automatically be enter to win anyone of the following:
Yeti Cooler, Amazon eGift Card, and Movie eGift Card!

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Suggested Solutions

Introduction I needed to skip over some file processing within a For...Next loop in some old production code and wished that VB (classic) had a statement that would drop down to the end of the current iteration, bypassing the statements that were c…
When designing a form there are several BorderStyles to choose from, all of which can be classified as either 'Fixed' or 'Sizable' and I'd guess that 'Fixed Single' or one of the other fixed types is the most popular choice. I assume it's the most p…
As developers, we are not limited to the functions provided by the VBA language. In addition, we can call the functions that are part of the Windows operating system. These functions are part of the Windows API (Application Programming Interface). U…
Get people started with the process of using Access VBA to control Outlook using automation, Microsoft Access can control other applications. An example is the ability to programmatically talk to Microsoft Outlook. Using automation, an Access applic…

738 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question