IsA not working with Select Case

PaulS

Summary

My framework loops through controls and based on what control it is, certain actions are taken.
I tried to use the Select Case combined with IsA, but it seems that I can't use this combination.
I have to use the if ... then ... elseif ... then
Since there are many controls to check I prefer to use Select Case.

For i As Integer = 0 To pc.ControlCount - 1
  c = pc.ControlAt(i)
  Select Case c # sa_Controltypes
    # *****************************************************
    Case IsA C_TextField # Textfield
      Select Case actiontype
        Case 1 # Populate
          C_TextField(c).InC = Me
          C_TextField(c).Dat = d.Lookup(C_TextField(c).RsFieldName, "")
          C_TextField(c).MaximumCharactersAllowed = modGlobal.DbMain.DbFieldLength(Data.TableName, C_TextField(c).RsFieldName)
        Case 2 # Cancel
          C_TextField(c).Dat = d.Lookup(C_TextField(c).RsFieldName, "")
        Case 3 # Validate - Only on 'Required'
          C_TextField(c).Validate()
        Case 4 # Update db
          d.Value(C_TextField(c).RsFieldName) = C_TextField(c).Dat.Replace("'", "''")
      End Select
    Else
     # Unknown control
  End Select
Next

Objo Studio Version

26.7.1

Operating System

Select the operating system(s) affected as tags for this post.
macOS

Steps To Reproduce

Expected Result

Actual Result

Screenshots, Logs, Or Sample Project

Problem using Select Case

No Problem using If ... IsA ... Then

bgrommes

Hm, I like this but for what it's worth, Buoy has just added a new Treat / End Treat construct:

treat thing as otherType
     // thing is othertype in this block
         NO CAST REQUIRED HERE
 else treat thing as yetAnotherType
      // thing is yetAnotherType in here
         NO CAST REQUIRED HERE
 else
     // thing is the original type here
 end treat

Personally I think "Select Case IsA whatever" solves the same problem without a new language construct, and with more clarity and simplicity -- so doing this would be advantageous relative to Buoy assuming it ends up getting anywhere near as far as Objo already is.

PaulS

I noticed that my for / next loop was wrong.
I should be

Var count As Integer = pc.Controls().Count
For Each child As Control In pc.Controls()
  ...
Next

The Select Case with IsA is still giving Unexpected token 'IsA'

Garry

Thanks Paul. This wasn’t user error.

IsA itself was working correctly, but Select Case didn’t yet support Case IsA TypeName syntax, so Unexpected token 'IsA' was coming from a missing parser feature.

I’ve added support for this now. In the next Objo Studio release, this pattern will work:

For Each child As Control In pc.Controls()
  Select Case child
  Case IsA C_TextField
    Var field As C_TextField = C_TextField(child)
    # ...
  Case IsA PushButton
    Var button As PushButton = PushButton(child)
    # ...
  Else
    # Unknown control
  End Select
Next

It also supports comma-separated type cases:

Case IsA TextField, IsA TextArea

The selector expression is evaluated once, cases are checked in order, and the first matching case wins. This uses the same runtime semantics as child IsA SomeType.

For now, in 26.7.1, keep using If child IsA ... Then / ElseIf, or Select Case True as a temporary workaround.

https://feedback.objo.dev/feature/680

Garry

Whilst adding Case IsA TypeName support, I also added Case lower To upper range syntax for Select Case.

In the next Objo Studio release this will work:

Select Case dayOfWeek
Case 0
    name = "Sunday"
Case 1
    name = "Monday"
Case 2 To 5
    name = "Midweek"
Case 6
    name = "Saturday"
Else
    name = "Unknown"
End Select

Ranges are inclusive, so Case 2 To 5 matches 2, 3, 4, and 5. They use the same ordering rules as >= and <=.

You can also mix ranges with comma-separated alternatives:

Select Case value
Case 1 To 5, 10 To 15
    Print("In range")
Else
    Print("Outside range")
End Select

The usual Select Case rules still apply: the selector expression is evaluated once, cases are checked in order, and the first matching case wins.

So the next release will support ordinary values, comma-separated values, comparison cases like Case Is >= 90, type cases like Case IsA TextField, and inclusive range cases like Case 2 To 5.