All,
I am setting-up a class module structure in VBA to add plans that have multiple milestones, but I'm quite new to it. I did the following:
A class module called 'Plan' that contains a 'name' property (string) and a 'Milestones' property (class Milestones).
This milestones class module is a collection of objects of a class module called 'Milestone'.
The 'Milestone' class has a 'name' property and a 'value' property.
So in my module I am now specifying the milestones for a specific plan:
Plan.Milestones.Add "MilestoneA", Cells(i, 5)
Plan.Milestones.Add "MilestoneB", Cells(i, 7)
...
Until now everything is fine. Now for MilestoneC I would like to know the value of MilestoneA. How do I get the value for the Milestone with name 'MilestoneA'.
I know the below code would give me the answer, but I don't want to hardcode 'item(1)' (I want to use the name):
Plan.Milestones.Item(1).Value
In the clsMilestones class:
Private prvt_Milestones As New Collection
Property Get Item(Index As Variant) As clsMilestone
Set Item = prvt_Milestones(Index)
End Property
Sub Add(param_Name As String, param_Value As String)
Dim new_milestone As clsMilestone
Set new_milestone = New clsMilestone
new_milestone.Name = param_Name
new_milestone.Value = param_Value
prvt_Milestones.Add new_milestone
End Sub
Your Milestones class is a collection class. By convention, collection classes have an Item property that is the class' default member. You can't easily specify a class' default member in VBA, but it's not impossible.
Export the code file, open it in Notepad. Locate your Public Property Get Item member and add a VB_UserMemId attribute - while you're there you can add a VB_Description attribute, too:
Public Property Get Item(ByVal Index As Variant) As Milestone
Attribute Item.VB_UserMemId = 0
Attribute Item.VB_Description = "Gets the item at the specified index, or with the specified name."
Set Item = prvt_Milestones(Index)
End Property
The UserMemId = 0 is what makes the property the class' default member - note that only one member in the class can have that value.
Don't save and close just yet.
You'll want to make your collection class work with a For Each loop too, and for that to work you'll need a NewEnum property that returns an IUnknown, with a number of attributes and flags:
Public Property Get NewEnum() As IUnknown
Attribute NewEnum.VB_Description = "Gets an enumerator that iterates through the collection."
Attribute NewEnum.VB_UserMemId = -4
Attribute NewEnum.VB_MemberFlags = "40"
Set NewEnum = prvt_Milestones.[_NewEnum]
End Property
Note that your internal encapsulated Collection has a hidden member with a name that begins with an underscore - that's illegal in VBA, so to invoke it you need to surround it with square brackets.
Now this code is legal:
Dim ms As Milestone
For Each ms In Plan.Milestones
Debug.Print ms.Name, ms.Value ', ms.DateDue, ...
Next
Save the file, close it, and re-import it into your project.
Since you're populating the collection using a string key (at least that's what your Add method seems to be doing), then the client code can use either the index or the key to retrieve an item.
And now that Item is the class' default member, this is now legal:
Set milestoneA = Plan.Milestones("Milestone A").Value
Note that your Add method needs to specify a value for the Key argument when adding to the internal collection - if you want the items keyed by Name, use the Name as a key:
Public Sub Add(ByVal Name As String, ByVal Value As Variant)
Dim new_milestone As Milestone
Set new_milestone = New Milestone
new_milestone.Name = Name
new_milestone.Value = Value
prvt_Milestones.Add new_milestone, Name
End Sub
Use a dictionary of Milestone classes in the plan class and set the key to be the "Milestone_x" and the item to be a milestone class
Then you can say Plan.Milestones("Milestone99")
Add a property to the Milestones class that returns the milestone based on the name:
Property Get SelectByName(strMilestoneName as string) as clsMilestone
Dim vIndex
'Add code here to find the index of the milestone in question
vIndex = ????????
Set SelectByName = prvt_Milestones(Index)
End Property
OR
Edit the Item Property to Allow selection by either Index or Name:
Property Get Item(Index As Variant) As clsMilestone
If isNumeric(Index) then
Set Item = prvt_Milestones(Index)
Else
'Find Item based on Name
Dim vIndex
vIndex = ?????
Set Item = prvt_Milestones(vIndex)
End If
End Property
Related
I have Class with bunch of Properties which looks almost the same.
If Not gXXXReady Then 'Check global boolean variable gXXXReady
call Object.SubProcedureYYY()
End If
set XXX = gXXX ' Use global variable as property value
End Property
What is differnet between these Properties is XXX and ``YYY`
Is there some way how to simplify this code? Something like:
Private Function UniversalGetFunc(ByVal VarName As String, ByVal MethodName As String)
If Not GetVarByName(VarName) Then
call Object.CallProcedureByName("SubProcedure" & MethodName)
End If
End Function
...
' Usage
Property Get XXX() As Collection
UniversalGetFunc("XXX", "YYY")
set XXX = gXXX
End Property
Where GetVarByName and CallProcedureByName are (obviously) fictitious functions. Object is same for all my Properties, so is not neccesary to pass it to UniversalGetFunc.
It is even possible with (Office VBA?)
Thank you!
PS: The
is there way how to make class working similar to Arrays?
Let's say, I have Class (e.g. Workers) where main property is array of the Workers, nothing else.
Then I'm filling the class as follows
Dim wks as new Workers
wks.add("Worker1")
wks.add("Worker2")
wks.add("Worker3")
Then in Workers Class module:
Private Workers as Variant
Public Function add(ByVal val As Variant) As Long
ReDim Preserve Workers(LBound(Workers) To UBound(Workers) + 1)
Workers(UBound(Workers)) = val
add = UBound(Workers) - LBound(Workers) +1
End Function
Workers representation -> {"Worker1", "Worker2", "Worker3"}
Then I want to access Worker by its index. I know, how to access it by e.g wks.getWorker(1) but what I want to do, is to access it directly by wks(1) which should return "Worker 1". Example above looks, that usual Array or Collection can be used, but I have many internal methods done, only what I'm missing is to access Workers property to read/write directly by its index number.
Is it possible?
Edit
After transfer to Collections, Class looks like:
Option Explicit
Private Workers As Collection
Private Sub Class_Initialize()
Set Workers = New Collection
End Sub
Public Function add(ByVal val As Variant) As Long
Workers.add val
End Function
Public Property Get Item(Index As Integer) As Variant
Item = Workers(Index)
End Property
Public Property Set Item(Index As Integer, Value As Variant)
Workers.Remove Index
Workers.add Value, Before:=Index
End Property
with hidden attributes Attribute Item.VB_UserMemId = 0 at Getter and Setter.
Getting works fine:
Dim wks As New Workers
wks.add "Worker1"
wks.add "Worker2"
wks.add "Worker3"
Debug.Print wks(2) ' <-- OK here
'wks(2) = "Second Worker" ' <-- By debugging this go to Getter not Setter and after Getter is done, it allerts with Runtime error '424': Object required
Set wks(2) = "Second Worker" ' <-- This alert immediately Compile error: Object required on "Second Worker" string
Debug.Print wks(2)
Prints "Worker2" into console, thanks for this, but still I'm not able to set a new value to the required Index of the Workers Collection.
You could use a default member in VBA. Though you can't make the default memeber directly through VBA editor, but you can use any text editor.
Export your class from VBA editor, i.e. File->Export File
Open your exported class in Notepad (or any text editor)
Add this attribute line on your method or property you want to make it default. Attribute Item.VB_UserMemId = 0
You can for example make getWorker default member as.
Public Function GetWorker(Index As Integer) As Worker
Attribute Item.VB_UserMemId = 0
GetWorker = Workers(Index)
End Function
you can then use it like.
Set wk = wks(1)
Here is some detail about default members
http://www.cpearson.com/excel/DefaultMember.aspx
Edits
An example to make Getter/Setter as default member
Public Property Get Item(Index as Integer) as Worker
Attribute Item.VB_UserMemId = 0
Set Item = Workers(Index)
End Property
Public Property Set Item(Index as Integer, Value as Worker)
Attribute Item.VB_UserMemId = 0
Set Workers(Index) = Value
End Property
I've searched all over to see if there is an easy answer to this question, but there doesn't seem to be...
I'm using Excel VBA 2003 (yes, I know it's out-of date, but I can't change this), and all I want to do is list the names and values of all the readable properties in a given custom class.
I'd like to do something like this:
Class definition (for class entitled cFooBar)
Option Explicit
Private pFoo As String
Private pBar As String
Public Property Get Foo() As String
Foo=pFoo
End Property
Public Property Get Bar() As String
Bar=pBar
End Property
Calling code
Dim myFooBar as cFooBar, P as Property
myFooBar=new cFooBar
For Each P in myFooBar.Properties
Debug.Print P.Name, P.Value
Next
Of course, this doesn't work because there doesn't seem to be a "Properties" collection member for custom classes (or at least not one that you can get at), and there isn't a "Property" type either.
Does anybody know a way around this?
TIA,
Campbell
As John mentions above, reflection is not supported in VBA. Here is a hack that I have used before. Basically you can create a Collection or Dictionary object to store your "properties" by name.
Option Explicit
Private pProperties As Object
Public Property Get Properties() As Object
Set Properties=pProperties
End Property
Public Property Let Properties(p as Object)
Set pProperties = p
End Property
Sub Class_Initialize()
Set pProperties = CreateObject("Scripting.Dictionary")
'Add/instantiate your properties here
pProperties("foo") = "this is foo"
pProperties("bar") = "this is bar"
End Sub
Calling code
Dim myFooBar As New cFooBar, P As Variant
For Each P In myFooBar.Properties.Keys()
Debug.Print P, myFooBar.Properties(P)
Next
I am working on a simple tool that will allow me to parse multiple CSV files and spit them out onto a fresh worksheet "merged" together. Here is my implementation (I've simplified it) and my issue:
Class A
private variables as types
property methods for accessing variables
Class B
private variables as types
property methods for accessing variables
Class C
Private cA as ClassA
Private cB as Collection 'Collection of ClassB
Class D - Part of my problem
Private cC as Collection 'Collection of ClassC
'Other member variables and their property get/lets
Public Sub AddA(A as ClassA)
If cC.Item(A.foo) is Nothing then
dim tempC as ClassC
set tempC = new ClassC
tempC.A = A
End if
End Sub
Main Module - Other half of my problem
Dim cC as New ClassC
'Initialize Class C, this all works fine
Dim tempA as ClassA
Set tempA = new ClassA
'Set tempA properties
cC.AddA tempA 'This is where my error is
I've tried passing it as ByVal and ByRef each gives me different errors ("byref argument type mismatch", "invalid procedure or argument", and "Object doesn't support this property or method"
I have no idea what to try next, I even tried the parenthesis "thing" that supposedly forces the parameter into either ByVal or ByRef, I can't remember, that was yesterday.
Thanks.
This line:
tempC.A = A
means "assing to A property of tempC object the value of the default property of the A object."
Your A object apparently doesn't have a default property.
What you actually meant was probably:
Set tempC.A = A
But even then, you can't access a private field A of C class from D class. Make the field public or create a public SetA() method on C class and call it from D.
I have been asked to modify an Excel sheet with some arcaic programming. I have decided to rewrite it rather then modify all of the many GOTO statments and static arrays. My background is in C# so it has been a bit of a challenge (note: I am sure the naming convention is bad, I am used to being able to use underscore to define private variables)
I am having trouble inializing an attribute of the type dictionary within a class that I have in a VBA application.
The shortened version of the class looks like this
Private pTerminalCode As String
Private pTerminalName As String
...... other attributes
Private pPayRoll As Dictionary
'Propeties
Public Property Get terminalCode() As String
terminalCode = pTerminalCode
End Property
Public Property Let terminalCode(Value As String)
pTerminalCode = Value
End Property
....... more properties
Public Property Get headCount() As Dictionary
headCount = pHeadCount
End Property
Public Property Let headCount(Value As Dictionary)
pHeadCount = Value
End Property
When I try to use the following I get the error "Argument not optional" within the Get property of the headCount() attribute.
Private Function PopulateTerminal()
Dim terminal As clsTerminal
Set terminal = New clsTerminal
terminal.terminalCode = "Wil"
terminal.headCount.Add "Company", 100
End Function
I assume somewhere I need to inialize the dictionary (i.e. = New Dictionary) however I am strugling with where to place it. In C# I do this in the constructor without issue, not sure what to do here.
Thanks
You can do it in the constructor of the VBA class, like so:-
Public Sub Class_Initialize()
Set myDictionary = New Dictionary
End Sub
Don't forget to always use the Set keyword when assigning an object reference, e.g.:-
Public Property Get Foo() As Dictionary
Set Foo = myDictionary
End Sub