Select case over IF

[thomasmcgeown]

In terms of speed, is it better to use select case or a series of IF statements?

If anyone can explain why one is quicker than the other (if it is) id appreciate it

Cheers

 

[mrmovie]

i would guess if you had one CASE statement than the IF statement would be quicker.
where the cross over occurs ie select case becomes quicker i couldnt say.(thats if it every does)

isnt the main advantage making your code easier to read and maintain?

regards,
vonmoyla

 

[Golom]

Select case is probably marginally faster because the compiler has a single value to compare on each Case clause. An "If" can of course evaluate completely different values in each successive "ElseIf" clause.

I agree with MrMovie however ... I doubt that the speed differences are much and the decision is usually about readability and maintainability rather than speed.

 

[vladk]

Put 2 buttons on the form, copy and paste this code and you will see the difference at the form's caption after clicking the buttons (just wait for up to a minute).

Option Explicit

Private Sub Command1_Click()
Dim i As Long
Dim a, b, c, d, e, f, g, h
Dim myStart As Date
Dim myEnd As Date

myStart = Now
For i = 0 To 99999999

If a = b Then

ElseIf a = c Then

ElseIf a = d Then

ElseIf a = e Then

ElseIf a = f Then

ElseIf a = g Then

ElseIf a = h Then

End If

Next i
myEnd = Now

Caption = DateDiff("s", myStart, myEnd)

End Sub

Private Sub Command2_Click()
Dim i As Long
Dim a, b, c, d, e, f, g, h
Dim myStart As Date
Dim myEnd As Date

myStart = Now
For i = 0 To 99999999

Select Case True
Case a = b

Case a = c

Case a = d

Case a = e

Case a = f

Case a = g

Case a = h

Case Else

End Select
Next i
myEnd = Now

Caption = DateDiff("s", myStart, myEnd)
End Sub