Property Statement

A property, also called field or attribute, characterizes a given object or piece of information. Properties can be used to control access to data. It is common use to include instructions at setting or reading time of properties. Code can vary from simple assignment to complex context dependant routines. Using Get, Let or Set accessers enforces properties' consistency when necessary.

warning

This statement requires Option Compatible to be placed before the executable program code in a module.


语法:

Property Get Statement diagram


         [Private | Public] Property Get name[char | As typename]
         End Property
      

Property Set Statement diagram


         [Private | Public] Property [Let | Set] name[char] [([Optional [ByRef | ByVal]]value[char | As typename])] [As typename]
         End Property
      

参数:

name: The property name.

argument: Value to be passed to the Property setter routine.

note

Property setters often use a single argument. Multiple arguments are equally accepted.


argument fragment

argument fragment


      {[Optional [ByRef|ByVal]]|ParamArray} argument {{As typename|char}[ = expression]|[()]As Variant}
    
Parameters

Optional: The argument is not mandatory.

ByRef: The argument is passed by reference. ByRef is the default.

ByVal: The argument is passed by value. Its value can be modified by the called routine.

char: Type declaration character.

typename: Primitive data type name. Library or module defined types can also be specified.

= expression: Specify a default value for the argument, matching its declared type. Optional is necessary for each argument specifying a default value.

ParamArray: Use ParamArray when the number of parameters is undetermined. A typical scenario is that of a Calc user-defined function. Using ParamArray should be limited to the last argument of a routine.

tip

UsingParamArray or = expression require Option Compatible to be placed before the executable program code in a module.


warning

When using Option VBASupport 1, Optional arguments with no default value (= expression) are initialized according to their data type, except if Variant.


typename fragment

primitive data types fragment


      {Boolean|Byte|Currency|Date|Double|Integer|Long|Object|Single|String|Variant}
    
char fragment

type declaration characters


      { % | & | ! | # | $ | @ }
    

Examples


      Option Compatible
      Sub Main
          ProductName = "Office"
          Print ProductName ' displays "LibreOffice"
      End Sub
      
      Private _office As String
      Property Get ProductName As String
          ProductName = _office
      End Property
      Property Let ProductName(value As String)
          _office = "Libre"& value
      End Property
      
tip

In the absence of Property Let or Property Set, Property Get helps define protected information, which can not be accidently altered by a foreign module:



      Option Compatible
      Public Property Get PathDelimiter As String ' Read-only variable
          Static this As String
          If this = "" Then : Select Case GetGuiType()
              Case 1 : this = ";" ' Windows
              Case 4 : this = ":" ' Linux or macOS
              Case Else : Error 423 ' Property or method not defined: PathDelimiter
          End Select : End If
          PathDelimiter = this
      End Property ' read-only PathDelimiter
      
      Sub Main
          PathDelimiter = "a sentence" ' does nothing
      End Sub
      
note

Use Let or Set when handling UNO services or class objects:



      Option Compatible
      Sub Main
          'Set anObject = CreateUnoService( "com.sun.star.frame.Desktop" )
          anObject = CreateUnoService( "com.sun.star.frame.Desktop" )
          Print anObject.SupportedServiceNames(0) ' displays "com.sun.star.frame.Frame"
      End Sub
      
      Property Get anObject As Object
          Set anObject = _obj
      End Property
      
      Private _obj As Object
      
      'Property Set anObject(value As Object)
          'Set _obj = value.CurrentFrame
      'End Property
      Property Let anObject(value As Object)
          Set _obj = value.CurrentFrame
      End Property
      

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