Property

{ 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

name of the Type or Class

fieldname

name of the property

new_value

the value passed to property to be assigned

index

the property index value

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