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.
Example
PROPERTY Enabled AS Boolean
PROPERTY READ Handle AS Integer
...
PRIVATE $bEnabled AS Boolean
PRIVATE $iHandle AS Integer
' Implements the Enabled property
FUNCTION Enabled_Read() AS Boolean
RETURN $bEnabled
END
SUB Enabled_Write(bEnabled AS Boolean)
$bEnabled = bEnabled
UpdateEverything
END
' Implements the Handle property
FUNCTION Handle_Read() AS Integer
RETURN $iHandle
END
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
End
Private Sub Name_Write(Value As String)
$sName = Value
End
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
End
See also