lang • propdecl

Property Declaration

PROPERTY [ READ ] Identifier AS Datatype

This declares a class property.

If the keyword READ is specified, then the property will be read-only.

Once declared, a property must be implemented: you must write a function to read the property, and if not read-only, a function to write the property.

The name of the read function is the name of the property followed by an underscore and the word Read. This function takes no arguments and must return data whose type is the same as the property datatype.

The name of the write function is the name of the property followed by an underscore and the word Write. This function is a procedure that returns nothing. It takes only one argument which has the same type as the property datatype.


PROPERTY Enabled AS Boolean

PRIVATE $bEnabled AS Boolean
PRIVATE $iHandle AS Integer

' Implements the Enabled property

FUNCTION Enabled_Read() AS Boolean

  RETURN $bEnabled


SUB Enabled_Write(bEnabled AS Boolean)

  $bEnabled = bEnabled


' Implements the Handle property

FUNCTION Handle_Read() AS Integer

  RETURN $iHandle


Property Synonymous

PROPERTY [ READ ] Identifier [ , Synonymous1 [ , Synonymous2 ... ] ] AS Datatype

Since 3.1

It is possible to declare up to three synonymous to the declared properties by using the second syntax.

Property shortcut

PROPERTY [ READ ] Identifier AS Datatype USE Variable

Since 3.14

This syntax declares a global private variable Variable that will be used for implementing the Identifier property.

Property Name As String Use $sName

is an exact equivalent of:

Property Name As String
Private $sName As String

Private Sub Name_Read() As String
  Return $sName

Private Sub Name_Write(Value As String)
  $sName = Value

If you need, you can override the Read or Write or both default property methods:

Property Name As String Use $sName

Private Sub Name_Write(Value As String)

  If Not Value Then Error.Raise("Incorrect name")
  $sName = Value


See also