{ Type | Class } typename

Declare Property fieldname () As datatype
Declare Property fieldname ( [ ByRef | ByVal ] new_value As datatype )
Declare Property fieldname ( [ ByRef | ByVal ] index As datatype ) As datatype
Declare Property fieldname ( [ ByRef | ByVal ] index As datatype, [ ByRef | ByVal ] new_value As datatype )

End { Type | Class }

Property typename.fieldname () As datatype

statements

End Property

Property typename.fieldname ( [ ByRef | ByVal ] new_value As datatype )

statements

End Property

Property typename.fieldname ( [ ByRef | ByVal ] index As datatype ) As datatype

statements

End Property

Property typename.fieldname ( [ ByRef | ByVal ] index As datatype, [ ByRef | ByVal ] new_value As datatype )

statements

End Property

typename
fieldname
new_value
index

Property fields are used to get and set values of a Type or Class in the same way as other data fields except instead of a simple assignment to a field or a value retrieved from field, a procedure is executed.

typename is the name of the type for which the Property method is declared and defined. Name resolution for typename follows the same rules as procedures when used in a Namespace.

A Property may optionally have one index parameter. When indexed, properties are accessed as Property(Index) = Value.

A hidden This parameter having the same type as typename is passed to the property procedure. This is used to access the fields of the Type or Class.

Type Vector2D
  As Single x, y
  Declare Operator Cast() As String
  Declare Property Length() As Single
  Declare Property Length( ByVal new_length As Single )
End Type

Operator Vector2D.cast () As String
  Return "(" + Str(x) + ", " + Str(y) + ")"
End Operator

Property Vector2D.Length() As Single
  Length = Sqr( x * x + y * y )
End Property

Property Vector2D.Length( ByVal new_length As Single )
  Dim m As Single = Length
  If m <> 0 Then
    '' new vector = old / length * new_length
    x *= new_length / m
    y *= new_length / m
  End If
End Property

Dim a As Vector2D = ( 3, 4 )

Print "a = "; a
Print "a.length = "; a.length
Print

a.length = 10

Print "a = "; a
Print "a.length = "; a.length

Output:

a = (3, 4)
a.length =  5

a = (6, 8)
a.length =  10

Property Indexing:

  '' True/False
Namespace BOOL
  Const FALSE = 0
  Const TRUE = Not FALSE
End Namespace

Type BitNum
  Num As UInteger
  
    '' Get/Set Properties each with an Index.
  Declare Property NumBit( ByVal Index As Integer ) As Integer
  Declare Property NumBit( ByVal Index As Integer, ByVal Value As Byte )
End Type

  '' Get a bit by it's index.
Property BitNum.NumBit( ByVal Index As Integer ) As Integer
  Return Bit( This.Num, Index )
End Property

  '' Set a bit by it's index.
Property BitNum.NumBit( ByVal Index As Integer, ByVal Value As Byte )

    '' Make sure index is in Integer range.
  If Index >= ( SizeOf(This.Num) * 8 ) Then
    Print "Out of uInteger Range!"
    Exit Property
  Else
    If Index < 0 Then Exit Property
  End If
  
  If Value = BOOL.FALSE Then
    This.Num = BitReset( This.Num, Index )
  End If
  
  If Value = BOOL.TRUE Then
    This.Num = BitSet( This.Num, Index )
  End If
  
End Property


Dim As BitNum Foo


Print "Testing property indexing with data types:"
Print "FOO Number's Value: " & Foo.Num

  '' Set the bit in the number as true.
Foo.NumBit(31) = BOOL.TRUE
Print "Set the 31st bit of FOO"

  '' Print to see if our bit has been changed.
Print "FOO Number's Value: " & Foo.Num
Print "FOO 31st Bit Set? " & Foo.NumBit(31)
Sleep
Print ""

Output:

Testing property indexing with data types:
FOO Number's Value: 0
Set the 31st bit of FOO
FOO Number's Value: 2147483648
FOO 31st Bit Set? -1

• Class
  
• Type