CODEWITHSUNDEEP
vbavbscript
user1925406
user1925406

Reputation: 733

Object based programming in Microsoft Vb script

I have one fundamental question in object based programming in vb script or VBA. In general when we use the object oriented programming in Java we use object references to either a variable or function, like:

Obj.Add() or Obj.i=5

But in VBA and VB scripting we use stuff like Obj.Property.Property or Obj.Method.Property like:

Set sib = Tchilds.item(j).childNodes 'where item is a method defined in DOM.

My doubt how is this logically possible.

Upvotes: 1

Views: 196

Answers (1)

Ekkehard.Horner
Ekkehard.Horner

Reputation: 38755

If you think of Properties as cousins of Subs/Functions/Methods (like getters/setters) then the mystery should vanish. The 'access object members' operator (dot) 'works' as long as on the left there is (a reference to) an object and on the right there is a valid member - method, variable/field, or property - name. Chaining dots 'works' as long as the x.y expressions evaluate to an object, so that in y.z z is a member of that object. The last one may be a non-object (no further dot on its right).

>> Set oFS = CreateObject("Scripting.FileSystemObject")
>> Set oFld = oFS.GetFolder(".") -- method .GetFolder returns Folder object
>> Set oFiles = oFld.Files -- Property .Files returns collection object
>> WScript.Echo oFiles.Count -- oFiles has a simple/non-object member .Count
>>
2
>> WScript.Echo oFiles.Count.ToString() -- .Count is not an object, but a number
>>
Error Number:       424
Error Description:  Object required
>> WScript.Echo oFS.GetFolder(".").Files.Count -- chaining
                obj obj            obj   var
>>
2

Upvotes: 2

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