Option explicit - Xtreme Visual Basic Talk

09-18-2002, 06:24 PM

Rotti

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Option explicit

Hello, guys,

Something about VB code I always confused myself, it's the Option Explicit on the top of every thing, could you pros give me a brief explanation?

1/. When I added this to the code, the one that worked would no longer work, mostly to do with var names
2/. When and how should I use it?
3/. What is the purpose of this?
4/. Any limitation on this?

Thanks a lot, guys.

09-18-2002, 06:27 PM

Spike

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1. It requires all variables to be declared
2. Always
3. To make sure you declare all your variables
4. What do you mean?

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09-18-2002, 06:33 PM

Rotti

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I mean if there is any time I should not use this.
Why should I always use this? eg, if I put a message box:

MyMessage = MsgBox("Hello World", 0, "Test")

That means I have to declare MyMessage as a var first?
Wouldn't that be a hassle? In the case I had above, what type of var I should declare as?

Thanks a lot.

09-18-2002, 06:51 PM

Spike

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Well, not declaring variables can lead to messy code, hard to find errors, and slow code.

In that senario, i would declare MyMessage as an Integer.

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09-18-2002, 06:52 PM

randtek

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For one thing, declaring all variables makes debugging easier, as it prevents errors caused by mistyping or misspelling variable names.

It really is not a hassle once you get in the habit. And it's much less hassle than struggling to find a strange error caused by a mistyped variable name. It is also just considered to be good programming practice.

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09-18-2002, 06:54 PM

orufet

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You can also declare MyMessage as vbMsgBoxResult.

09-18-2002, 06:55 PM

Rotti

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Thanks a lot, guys!

09-18-2002, 08:05 PM

MarkVB6

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Further question

What happens when you want to use the split command?

Because if you have to declare the variable that the split array is going to be placed into, what should you declare it as? An array won't work, and neither will a non-array. So how would you work split around Option Explicit?

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09-18-2002, 08:13 PM

Pookie

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An example on how to use split

Code:

Option Explicit

Dim strString as String
Dim Data() as String

strString="A B C D E"
Data = Split(strString," ")
Debug.Print Data(3)

Result of Debug.Print = "D"

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#10

09-18-2002, 08:20 PM

MarkVB6

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Ahh i see you just leave a blank array like Data(). Never learned those kind of basics...though I knew how to use split.

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09-18-2002, 08:22 PM

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A blank data in an array means it gets declared dynamically, which mean you can change it's size at any time.
eg:

Code:

Dim a() as Long
Redim a(9) ' give it 10 elements
Redim Preserve a(4) ' give it 5 elements, can keep the info
Erase a() ' release the memory

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#12

09-19-2002, 02:47 AM

BillSoo

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And if you really wanted to...you could define a VARIANT explicitly. Without OPTION EXPLICIT, any unknown variable was assumed to be a variant. But you could just say:

dim v as variant

v = split(sString," ")

and v will be a variant that contains the string array.

However, a lot of people frown on variants, myself included. It's usually better to simply define the type you need instead of relying on the behaviour of a variant.

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