What happens to Select Case <string> ?

General
1

I have:

[code]Dim FirstName As String

FirstName = “Emile”

Select Case FirstName[/code]

etc.

and at run time I get:

Type mismatch error. Expected String, but got boolean.

Why ?

I quit Xojo and reload it to the same error.

Xojo 2014r2.1
Os X 10.9.5

2

Looks ok so far. How do you compare your case statements? Do you “End” the Select Case block?

3

[quote=144629:@Emile Schwarz]and at run time I get:

Type mismatch error. Expected String, but got boolean.
Why ?

[/quote]

You should post the entire code. I bet you did something like :

Dim FirstName As String FirstName = "Emile" Select Case FirstName case FirstName = "Emile" // This is a boolean

What you want to do is :

Dim FirstName As String FirstName = "Emile" Select Case FirstName case "Emile"

4

[code]Dim FirstName As String

FirstName = “Emile”

Select Case FirstName

Case “Emile”
// Do something

Case “Albert”
// Do something

Case “Roger”
// Do something

Case Right(“Emile”,1) = “e”
// Do something different

Case InStr(FirstName,“S”)
// Do something different

Else
// Not found

End Select[/code]

Sorry, I was thinking the shared code was enough since the error goes to Select Case testExpression
Or… I may forgot to say something important.

Select Case.

OK: because both answers ask for more data, I tried some more tests and found working cases:

Case “1”
Case “August”

Compiles.

The following produce the error message
Case FirstName = “Emile”
Case Right(FirstName,1) = “e”

OK (BIS): I now understand the error. In both cases above, the result of the evaluation is a Boolean !

Thanks, I got it. It was 5:30 (on a 24 Hours Clock) when I wrote that. I replaced the Select Case Block by an If … ElseIf… Block with many empty lines and it is as clear as a Select Case and works fine !

I wasted one hour on this simple… “error”.

BTW: is the IDE report cautionable ?
(it shows the error in the Select Case line instead of in the Case line(s))

PS: I checked on a C++ for Dummies book switch(expression) and found nothing except a ‘bug’ in the 2002 edition: they used in the example ‘cas’ instead of ‘case’. Certainly a translation error.

5

Roger, Michel:

Thank you for your answers. Roger says that Select Case works and Michel also ask for code; this leads me to “think different” and found where the error lies (my error).

6

You could also write it as a combination of Select Case and If Then:

[code]Dim FirstName As String

FirstName = “Emile”

Select Case FirstName

Case “Emile”
// Do something

Case “Albert”
// Do something

Case “Roger”
// Do something

Else
If Right(Firstname,1) = “e”
// Do something different

elseif InStr(FirstName,“S”)>0
// Do something different

Else
// Not found
End If

End Select[/code]

7

Thank you Jrmie.

8

Another option:

select case true
case FirstName = "Emile"
case FirstName.Right( 1 ) = "e"
…
9

[quote=144664:@Kem Tekinay]Another option:

select case true case FirstName = "Emile" case FirstName.Right( 1 ) = "e" … [/quote]

Kem, have no idea you can do that…

10

Me too !!!

Worst, it took me times to understand what I read: Select Case True My brain escaped True !!!

Nota: I choosed Select Case because its reading is far better than an If / End If block…
But after adding extra spaces in the Select Case converted to If / End If code, it happens that the new code is as readable as the previous one.

Another question: do we know if there is a difference between these two ways of doing things ( Select Case vs If / End If ) in speed ?

11

Regarding speed it depends actually.

Select Case is quicker when you evaluate a function but If/End If is quicker if you evaluate a property.

For example:

Function evaluateString(str As String) //Takes 100ms to evaluate Return str End Function

If evaluateString("toto") = "123" then //Do something Elseif evaluateString("toto") = "456" //Do something else End If

Select Case evaluateString("toto")
Case "123"
//Do something
Case "345"
//Do something else
End Case

Select Case is quicker because it calls evaluateString only once.

12

Good point.

13

[quote=144865:@JrmieLeroy]Regarding speed it depends actually.

Select Case is quicker when you evaluate a function but If/End If is quicker if you evaluate a property.

For example:

Function evaluateString(str As String) //Takes 100ms to evaluate Return str End Function

If evaluateString("toto") = "123" then //Do something Elseif evaluateString("toto") = "456" //Do something else End If

Select Case evaluateString("toto")
Case "123"
//Do something
Case "345"
//Do something else
End Case

Select Case is quicker because it calls evaluateString only once.[/quote]
But you could store the value of evaluateString in a variable, which would mean that you only have to call it once.

‘select case’ vs ‘if … else’ has an innegligible difference in speed when running. Choosing between the two should depend on how easy the code is to read and write.

14 
If evaluateString("toto") = "123" then
//Do something
Elseif evaluateString("toto") = "456" then
//Do something else
End If

If it is worth the optimization I would personally write the code like this:

dim evaluateStringToTo as string = evaluateString("toto")
If evaluateStringToTo= "123" then
//Do something
Elseif evaluateStringToTo = "456" then
//Do something else
End If
15

Adding empty lines before each and every ElseIf / Else add clarity / readability to the whole if block and that is what I was searching initially / why I choosed Select Case.

Then, I was wrong in my logic :frowning: