Properties
属性是成员变量和成员过程的特殊组合。它们提供了通过正常查看的赋值或成员访问来设置或检索对象的值的方法，但是如果需要更新自身，则还允许对象执行操作。
基本属性
声明和使用setter和getter属性。
索引属性
具有附加参数的属性。
基本属性
声明类似于会员程序的资源，但使用属性关键字而不是Sub或Function.例如，让我们考虑窗口系统或GUI库的窗口类。
Type Window
Private:
As String title_
End Type
Dim As Window w
Private:
As String title_
End Type
Dim As Window w
为了设置窗口的标题，可以添加setter 属性：
Type Window
Declare Property title(ByRef s As String)
Private:
As String title_
End Type
Property Window.title(ByRef s As String)
this.title_ = s
End Property
Dim As Window w
w.title = "My Window"
Declare Property title(ByRef s As String)
Private:
As String title_
End Type
Property Window.title(ByRef s As String)
this.title_ = s
End Property
Dim As Window w
w.title = "My Window"
它与成员子非常相似，因为它需要参数并根据参数将对象更新为新状态。但是，发送此参数的语法是基本赋值，而不是函数调用。通过将新值赋值给title属性，属性过程将自动使用给定的新值进行调用，并可更新窗口以反映更改。对象如何在内部表示属性状态。
通过设计，属性一次只能赋值一个值，因此属性过程不能有多个参数。
设置窗口标题后，也可以检索它。以下是添加getter 属性的方法：
Type Window
'' setter
Declare Property title(ByRef s As String)
'' getter
Declare Property title() As String
Private:
As String title_
End Type
'' setter
Property Window.title(ByRef s As String)
this.title_ = s
End Property
'' getter
Property Window.title() As String
Return this.title_
End Property
Dim As Window w
w.title = "My Window"
Print w.title
'' setter
Declare Property title(ByRef s As String)
'' getter
Declare Property title() As String
Private:
As String title_
End Type
'' setter
Property Window.title(ByRef s As String)
this.title_ = s
End Property
'' getter
Property Window.title() As String
Return this.title_
End Property
Dim As Window w
w.title = "My Window"
Print w.title
吸气剂非常类似于功能.它应该返回属性的当前值，并且允许当前值根据需要从其他内部值计算。请注意，setter 和getter 使用相同的标识符，表示它们处理相同的属性。
就像方法重载一样，可以指定多个设置器，前提是它们具有不同的参数类型：
Type Window
Declare Property title(ByRef s As String)
Declare Property title(ByVal i As Integer)
Declare Property title() As String
Private:
As String title_
End Type
Property Window.title(ByRef s As String)
this.title_ = s
End Property
Property Window.title(ByVal i As Integer)
this.title_ = "Number: " & i
End Property
Property Window.title() As String
Return this.title_
End Property
Dim As Window w
w.title = "My Window"
Print w.title
w.title = 5
Print w.title
Declare Property title(ByRef s As String)
Declare Property title(ByVal i As Integer)
Declare Property title() As String
Private:
As String title_
End Type
Property Window.title(ByRef s As String)
this.title_ = s
End Property
Property Window.title(ByVal i As Integer)
this.title_ = "Number: " & i
End Property
Property Window.title() As String
Return this.title_
End Property
Dim As Window w
w.title = "My Window"
Print w.title
w.title = 5
Print w.title
与这个属性的例子相比，这里是不使用属性的类似的代码：
Type Window
Declare Sub set_title(ByRef s As String)
Declare Sub set_title(ByVal i As Integer)
Declare Function get_title() As String
Private:
As String title
End Type
Sub Window.set_title(ByRef s As String)
this.title = s
End Sub
Sub Window.set_title(ByVal i As Integer)
this.title = "Number: " & i
End Sub
Function Window.get_title() As String
Return this.title
End Function
Dim As Window w
w.set_title("My Window")
Print w.get_title()
w.set_title(5)
Print w.get_title()
Declare Sub set_title(ByRef s As String)
Declare Sub set_title(ByVal i As Integer)
Declare Function get_title() As String
Private:
As String title
End Type
Sub Window.set_title(ByRef s As String)
this.title = s
End Sub
Sub Window.set_title(ByVal i As Integer)
this.title = "Number: " & i
End Sub
Function Window.get_title() As String
Return this.title
End Function
Dim As Window w
w.set_title("My Window")
Print w.get_title()
w.set_title(5)
Print w.get_title()
代码基本相同，只有语法不同。属性专门设计用于将setter / getter概念和语言的正常方法（赋值和访问）的值组合到一个类的成员变量中。程序员可以决定他们喜欢哪种方式。
这是一个示例，演示文本用户界面窗口类，允许使用属性设置位置和标题：
Namespace tui
Type Point
Dim As Integer x, y
End Type
Type char
Dim As UByte value
Dim As UByte Color
End Type
Type Window
'' public
Declare Constructor _
( _
x As Integer = 1, y As Integer = 1, _
w As Integer = 20, h As Integer = 5, _
title As ZString Ptr = 0 _
)
Declare Destructor
Declare Sub show
'' title property
Declare Property title As String
Declare Property title( new_title As String )
'' position properties
Declare Property x As Integer
Declare Property x( new_x As Integer )
Declare Property y As Integer
Declare Property y( new_y As Integer )
Private:
Declare Sub redraw
Declare Sub remove
Declare Sub drawtitle
Dim As String p_title
Dim As Point Pos
Dim As Point siz
End Type
Constructor Window _
( _
x_ As Integer, y_ As Integer, _
w_ As Integer, h_ As Integer, _
title_ As ZString Ptr _
)
pos.x = x_
pos.y = y_
siz.x = w_
siz.y = h_
If( title_ = 0 ) Then
title_ = @"untitled"
End If
p_title = *title_
End Constructor
Destructor Window
Color 7, 0
Cls
End Destructor
Property window.title As String
title = p_title
End Property
Property window.title( new_title As String )
p_title = new_title
drawtitle
End Property
Property window.x As Integer
Return pos.x
End Property
Property window.x( new_x As Integer )
remove
pos.x = new_x
redraw
End Property
Property window.y As Integer
Property = pos.y
End Property
Property window.y( new_y As Integer )
remove
pos.y = new_y
redraw
End Property
Sub window.show
redraw
End Sub
Sub window.drawtitle
Locate pos.y, pos.x
Color 15, 1
Print Space( siz.x );
Locate pos.y, pos.x + (siz.x \ 2) - (Len( p_title ) \ 2)
Print p_title;
End Sub
Sub window.remove
Color 0, 0
Var sp = Space( siz.x )
For i As Integer = pos.y To pos.y + siz.y - 1
Locate i, pos.x
Print sp;
Next
End Sub
Sub window.redraw
drawtitle
Color 8, 7
Var sp = Space( siz.x )
For i As Integer = pos.y + 1 To pos.y + siz.y - 1
Locate i, pos.x
Print sp;
Next
End Sub
End Namespace
Dim win As tui.window = tui.window( 3, 5, 50, 15 )
win.show
Sleep 500
win.title = "Window 1"
Sleep 250
win.x = win.x + 10
Sleep 250
win.title = "Window 2"
Sleep 250
win.y = win.y - 2
Sleep 250
Locate 25, 1
Color 7, 0
Print "Press any key...";
Sleep
Type Point
Dim As Integer x, y
End Type
Type char
Dim As UByte value
Dim As UByte Color
End Type
Type Window
'' public
Declare Constructor _
( _
x As Integer = 1, y As Integer = 1, _
w As Integer = 20, h As Integer = 5, _
title As ZString Ptr = 0 _
)
Declare Destructor
Declare Sub show
'' title property
Declare Property title As String
Declare Property title( new_title As String )
'' position properties
Declare Property x As Integer
Declare Property x( new_x As Integer )
Declare Property y As Integer
Declare Property y( new_y As Integer )
Private:
Declare Sub redraw
Declare Sub remove
Declare Sub drawtitle
Dim As String p_title
Dim As Point Pos
Dim As Point siz
End Type
Constructor Window _
( _
x_ As Integer, y_ As Integer, _
w_ As Integer, h_ As Integer, _
title_ As ZString Ptr _
)
pos.x = x_
pos.y = y_
siz.x = w_
siz.y = h_
If( title_ = 0 ) Then
title_ = @"untitled"
End If
p_title = *title_
End Constructor
Destructor Window
Color 7, 0
Cls
End Destructor
Property window.title As String
title = p_title
End Property
Property window.title( new_title As String )
p_title = new_title
drawtitle
End Property
Property window.x As Integer
Return pos.x
End Property
Property window.x( new_x As Integer )
remove
pos.x = new_x
redraw
End Property
Property window.y As Integer
Property = pos.y
End Property
Property window.y( new_y As Integer )
remove
pos.y = new_y
redraw
End Property
Sub window.show
redraw
End Sub
Sub window.drawtitle
Locate pos.y, pos.x
Color 15, 1
Print Space( siz.x );
Locate pos.y, pos.x + (siz.x \ 2) - (Len( p_title ) \ 2)
Print p_title;
End Sub
Sub window.remove
Color 0, 0
Var sp = Space( siz.x )
For i As Integer = pos.y To pos.y + siz.y - 1
Locate i, pos.x
Print sp;
Next
End Sub
Sub window.redraw
drawtitle
Color 8, 7
Var sp = Space( siz.x )
For i As Integer = pos.y + 1 To pos.y + siz.y - 1
Locate i, pos.x
Print sp;
Next
End Sub
End Namespace
Dim win As tui.window = tui.window( 3, 5, 50, 15 )
win.show
Sleep 500
win.title = "Window 1"
Sleep 250
win.x = win.x + 10
Sleep 250
win.title = "Window 2"
Sleep 250
win.y = win.y - 2
Sleep 250
Locate 25, 1
Color 7, 0
Print "Press any key...";
Sleep
请注意，如何更新窗口的位置或标题自动导致重新绘制窗口。
索引属性
属性可以有一个称为index的附加参数（目前只允许一个附加参数）。索引在属性名称后面的括号中指定，就像该属性是一个数组（只有一个维度）一样。例如：
Type IntArray
'' setters
Declare Property value(index As Integer, v As Integer)
Declare Property value(index As String, v As Integer)
Declare Property value(index As Integer, v As String)
Declare Property value(index As String, v As String)
'' getters
Declare Property value(index As Integer) As Integer
Declare Property value(index As String) As Integer
Private:
Dim As Integer data_(0 To 9)
End Type
Property IntArray.value(index As Integer) As Integer
Return This.data_(index)
End Property
Property IntArray.value(index As String) As Integer
Return This.data_(CInt(index))
End Property
Property IntArray.value(index As Integer, v As Integer)
This.data_(index) = v
End Property
Property IntArray.value(index As String, v As Integer)
This.data_(CInt(index)) = v
End Property
Property IntArray.value(index As Integer, v As String)
This.data_(index) = CInt(v)
End Property
Property IntArray.value(index As String, v As String)
This.data_(CInt(index)) = CInt(v)
End Property
Dim a As IntArray
a.value(0) = 1234
a.value("1") = 5678
a.value(2) = "-1234"
a.value("3") = "-5678"
Print a.value(0)
Print a.value("1")
Print a.value(2)
Print a.value("3")
Sleep
'' setters
Declare Property value(index As Integer, v As Integer)
Declare Property value(index As String, v As Integer)
Declare Property value(index As Integer, v As String)
Declare Property value(index As String, v As String)
'' getters
Declare Property value(index As Integer) As Integer
Declare Property value(index As String) As Integer
Private:
Dim As Integer data_(0 To 9)
End Type
Property IntArray.value(index As Integer) As Integer
Return This.data_(index)
End Property
Property IntArray.value(index As String) As Integer
Return This.data_(CInt(index))
End Property
Property IntArray.value(index As Integer, v As Integer)
This.data_(index) = v
End Property
Property IntArray.value(index As String, v As Integer)
This.data_(CInt(index)) = v
End Property
Property IntArray.value(index As Integer, v As String)
This.data_(index) = CInt(v)
End Property
Property IntArray.value(index As String, v As String)
This.data_(CInt(index)) = CInt(v)
End Property
Dim a As IntArray
a.value(0) = 1234
a.value("1") = 5678
a.value(2) = "-1234"
a.value("3") = "-5678"
Print a.value(0)
Print a.value("1")
Print a.value(2)
Print a.value("3")
Sleep