Enums and integers

I never quite understood why Xojo enums could not be type equivalent to their underlying integer type and I get caught out by the compiler most every time I use them.

I’m getting a little bored of typing integer every time i want to pass an enum to the framework and was wondering, is there a more elegant way than a clumsy explicit cast?

For instance…

ListBox2.HeaderAt(Integer(eColumns.columnName)) = ListBox1.HeaderAt(Integer(eFields.fieldName))

My first thought was to override the HeaderAt function. The following works fine for retrieving a value

MySubClassedListBox.HeaderAt(index as eColumns)
  Return HeaderAt(Integer(index))
End Function

Where I’m stuck is coming up with a matching assignment method. Is there a way to assign to HeaderAt using an enum as the index without breaking the assignment syntax?

It may be I’m being dumb here and missing something obvious. (I spend too much time using other development dialects these days.)

You could define an Extends method for your enum:

Function ToInteger (Extends v As eColumns) As Integer
  return integer( v )
End Function

// Elsewhere...
ListBox2.HeaderAt( eColumns.columnName.ToInteger ) = ...

(I haven’t tried this specific technique.)

Use the Assigns keyword to convert the last parameter in a method signature into a value being assigned:

MySubClassedListBox.HeaderAt(index as eColumns, Assigns NewValue As String)
  HeaderAt(Integer(index)) = NewValue
End Function

Calling syntax:

MySubClassedListBox.HeaderAt(enumvalue) = "Hello"
1 Like

You could also use Constants.

1 Like

Xojo enums are so mind boggling that I totally gave up on them. Constants are fine, they auto-complete, and are clearly understandable long after the code has been written. I group them with prefixes for a sort of pseudo-enum functionality.

Thank you @Andrew_Lambert. That looks like the magic rune I was searching for. And thank you all for your attention.

Yes I could use constants and I was using constants but the logical description of the problem fits an enum; a set of ordered values with an arbitrary identifier. I would much rather have clunky enums than no enums at all.

Enums should gain special properties in Xojo, to add more value to the language, and fix the current aberration of “binary enums” that aren’t enums and can’t be used anywhere.

Proposal:

1 Like

We need true type enums like C/C++ which can be converted and processed the same way. That way developing wrappers etc and faster code is much better.

The binary doesn’t work the same way.
“Typed List” will kinda act like it more but still is not the actual thing

If you use the above example as is, you need a function as

Function f( p As TableWhateverFields) // will only be restricted to such enum

To call a

f( TableWhateverFields.second ) // Needs conversion in the function to get the value 1

But if set typed list ON, you can generalize f() as

Function f( p As Integer) // any enum typed list returning an Integer is accepted

And retro compatibility with old functions is maintained, as such kind of need in the OP example:

ListBox2.HeaderAt(eColumns.columnName) = ListBox1.HeaderAt(eFields.fieldName)

And of course, a week after writing that I’ve fully embraced Enums and am implementing them left and right in all my projects, lol. They are indeed useful.

3 Likes
Forum for Xojo Programming Language and IDE. Copyright © 2021 Xojo, Inc.