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Collection Class module
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<H2>Introduction</H2>
Two Files in this article. coll.asp is the collection library, main.asp is the sample of using the collection class.
<H2>Sample Demo Page</H2>
<%
'------------------------------------------------------------------------------
'This is a sample of how to use the collection Class
'------------------------------------------------------------------------------
'Warning: This sample is using the Functionality provided by VBScript 5.x to
'install VBScript 5.x install IE5 or visit www.microsoft.com/vbscript
'------------------------------------------------------------------------------
%>
<!-- #include file="coll.asp"-->
<%
'----------------------------------------------------
'this is Our Object Class that we want to make
'a collection of
'----------------------------------------------------
Class Customer
Public Name
'i've only used one property to keep the class simple
' this class can have as many properties or method needed
'etc...
End Class
Dim oCustomers,i
'create Our Collections class
Set oCustomers = new Collection
'----------------------------------------------------
'just add all the item that you want
'into the collection
'----------------------------------------------------
'change the add function to take as many parameters as you want.
'refer to the [TODO] section in the Add function implementation
oCustomers.Add("Sarah")
oCustomers.Add("Sam")
oCustomers.Add("Dolly")
oCustomers.Add("Shadi")
oCustomers.Add("Becky")
oCustomers.Add("Licky")
'Enumerate through the collection
'Our collection class has the Count Property
For i=0 to oCustomers.Count-1
'to access an item in our collection use the Item
'function to return the object and VBScripts late binding's
'functionality to access it's Properties
Response.Write oCustomers.Item(i).Name & "<br>"
Next
'This is an example of removing an element
'from our Collection
oCustomers.Remove(3)
Response.Write "<hr>"
'Enumerate through the collection to show the New Content
'after the remove.
For i=0 to oCustomers.Count-1
Response.Write oCustomers.Item(i).Name & "<br>"
Next
'delete the instance of the Collection
'free up resources.
Set oCustomers = Nothing
%>
<H2>Collection page Code</H2>
<%
'------------------------------------------------------------------------------
'This is the collection include that implements the Collection Class.
'this file must be included into the page that wants to use the collection
'service.
'------------------------------------------------------------------------------
'Warning: This sample is using the Functionality provided by VBScript 5.x to
'install VBScript 5.x install IE5 or visit www.microsoft.com/vbscript
'------------------------------------------------------------------------------
'-----------------------------------------
' Class: Node
' Description: This class is used internally by the collection class to hold the
' the list of all objects in the list.
'-----------------------------------------
'Note: this class should NOT! be modified.
'-----------------------------------------
Class Node
Public Node
Public pNext
End Class
'----------------------------------------------------------------------------------
' Class: Collection
' Description: This is our Collection class.
' Create an object of this class and modify it's
' Add functon's TODO section to hold a collections
' of any user defined object.
'----------------------------------------------------------------------------------
'Note: Only the Add function should be modifid in this class.
'----------------------------------------------------------------------------------
Class Collection
'this is the member of the link list
'usd by the class to add its objects to.
Private m_list
'-------------------------
'Function: Display
'-------------------------
'internally used to debug
'-------------------------
Private Function Display()
Dim opal
'set our pointer to the start of the listy
Set opal = m_list
'loop until the end
Do While(IsObject(opal))
'output the information in the Node;
'[TODO]: Modify this to output anyinformation
'example response.write opal.Node.xxxxx
'where xxxxx is any property of your object.
Response.Write opal.Node.Name & "<br>"
'make sure that the next node is an object
if(Not IsObject(opal.pNext)) then
exit Do
End if
'move next
Set opal = opal.pNext
Loop
End function
'----------------------------------------------------
'This function adds to the collection
'change this function to add more parameters, that
'will set properties in your object
'----------------------------------------------------
'example Add(property1,property2,property3,etc..
'where: property[1-3] are properties of your class
'----------------------------------------------------
Public Function Add(szName)
'[TODO] change this to a variable of your class
'example Dim oMyclass
Dim oCustomer
Dim oNode,opal
'is the list empty
if Not IsObject(m_list) then
'the list is empty create an object
'of the user defined class
'[TODO] change from Customer to any
'user defined class.
Set oCustomer = new Customer
'[TODO] change this to assign arguments of interest.
oCustomer.Name = szName
'create a new node
Set m_list =new Node
'assign our new node to the list
Set m_list.Node = oCustomer
Else
'the list is not empty so just add to it
Set opal = m_list
'loop until the last node.
Do While(IsObject(opal))
if(Not IsObject(opal.pNext)) then
exit Do
End if
Set opal = opal.pNext
Loop
'we are at the end instatiate our class
'assign our arguments and add to the list
'[TODO] modify to suit accordingly
Set oCustomer =new Customer
oCustomer.Name = szName
Set oNode = new Node
'insert into the end of the list
Set oNode.Node = oCustomer
oNode.pNext = opal.pNext
Set opal.pNext = oNode
End if
End Function
'----------------------------------------------------
'This function if you are a C++ person is the destructor
'this is an event that gets called when the class terminates
'----------------------------------------------------
Private Sub Collection_Terminate()
'free all my resources.
Call Me.Free()
End Sub
'----------------------------------------------------
'Free
'----------------------------------------------------
Private Function Free()
Dim opal,opalNext
Set opal = m_list
'loop through the list and free Nodes.
Do While(IsObject(opal))
if(Not IsObject(opal.pNext)) then
exit Do
End if
Set opalNext = opal.pNext
Set opal = Nothing
Set opal = opalNext
Loop
Set opal = Nothing
End Function
'----------------------------------------------------
'Count This property get you the Collection Count
'----------------------------------------------------
Property Get Count()
Dim opal,i
Set opal = m_list
'loop through the list and Count it's Nodes.
Do While(IsObject(opal))
i = i + 1
if(Not IsObject(opal.pNext)) then
exit Do
End if
Set opal = opal.pNext
Loop
Count = i
End Property
'----------------------------------------------------
'InternalItem this function is used internally to return
'a reference to an items Node. this defers from Item
'because Item returns a reference to the Items object
'----------------------------------------------------
Private Function InternalItem(index)
Dim opal,i,obj
Set opal = m_list
i = 0
Do While(IsObject(opal))
if index = i then
Set obj = opal
exit Do
else
i = i + 1
End if
if(Not IsObject(opal.pNext)) then
exit Do
End if
Set opal = opal.pNext
Loop
if Not IsObject(obj) then
InternalItem = Null
Else
Set InternalItem = obj
End if
End Function
'----------------------------------------------------
'Item this function return the object of the index.
'----------------------------------------------------
Function Item(index)
Dim opal,i,obj
Set opal = m_list
i = 0
Do While(IsObject(opal))
if index = i then
Set obj = opal.Node
exit Do
else
i = i + 1
End if
if(Not IsObject(opal.pNext)) then
exit Do
End if
Set opal = opal.pNext
Loop
if Not IsObject(obj) then
Set Item = Null
Else
Set Item = obj
End if
End Function
'----------------------------------------------------
'Remove this function removes an item from the collection
'----------------------------------------------------
Function Remove(index)
Dim oPrev,opal,oNext
if index = 0 then
if IsObject(m_list.pNext) then
Set oNext = m_list.pNext
Set m_list = oNext
else
Set m_list = Nothing
End if
elseif index > 0 And index <= Me.Count() then
'we use InternalItem because we want a
'refernce to the Node not the object
Set oPrev = InternalItem(index-1)
Set opal = InternalItem(index)
if IsObject(opal.pNext) then
Set oPrev.pNext = opal.pNext
Else
oPrev.pNext = NULL
End if
Set opal = Nothing
End if
End Function
End Class %>
<H2>Summary</H2>
These demo file can be use as example how to use collection class module in vb.
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