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I'm using Excel VBA 2003 (yes, I know it's out-of date, but I can't change this), and all I want to do is list the names and values of all the readable properties in a given custom class.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
Related
I've been wrestling with this problem for a while. My problem is that I have a bunch of JSON data and I want to represent it as objects.
Arrays are problematic.
I create a class module such as FancyCat with a public Name as String for its name.
Then I can set this with
Dim MyFancyCat as FancyCat
Set MyFancyCat = new FancyCat
FancyCat.Name = JSONData("Name")
I've typed that from memory but I think it's correct. Anyhoo, it works fine.
The problem is that a fancy cat has several pairs of socks. The number of socks is variable.
In vba you cannot for some reason have a public array. So this code is illegal:
public Socks() as FancySock 'Illegal
Looking on SO I found two solutions, one, to make it private and use a property to access it, and the other, to declare it as Variant and then stick an array into it later.
My approach to populating this array, is to examine the JSON array to get the Count, and then to ReDim the array to match and then populate it.
The problem is my ReDim statement refuses to work.
It seems I cannot redim a property, I get an error. And I also get an error trying to redim the public variant field. My ReDim works OK if I declare a local array and redim it, so potentially I could do that and then assign it to the property... but it just seems bizarre that I can't redim it directly.
Any idea why it's not working?
With the Variant approach above my code is:
ReDim MyFancyCat.Socks(socksLength) As FancySocks
And in the FancyCat class module:
public Socks As Variant
I get Method or Data Member Not Found.
The error for the other approach was different but I rejigged all my code to try the second approach so I am not sure what it was.
Edit: I'm gonna explain what I am trying to do a bit more clearly. I have some JSON data coming in, and I want to store it as an object hierarchy.
In C# I would do this (pseudo code without linq shortcuts):
var myData = ReadJsonData(); // Produces a kind of dictionary
var myFancyCat = new FancyCat();
myFancyCat.Name = myData["Name"];
myFancyCat.Age = myData["Age"];
myFancyCat.Socks = new List<FancySock>();
foreach (var sock in myData["Socks"])
{
myFancyCat.Socks.Add(sock);
}
In excel I want to do the same thing.
So I make a class module for FancyCat and FancySock and give FancyCat public members for Name, Age etc but then I also want an array of socks that my cat owns. I wanted to do this with strongly typed references, e.g. my c# code above I can do:
myFancyCat.Socks[0].Colour // Intellisense works, shows colour as a property
However it seems in excel you can't have publicly declared arrays. So you can get around this according to the comments by declaring it as variant and then sticking an array in anyway, but you would lose the intellisense. Or you can use a get/let property which kinda works but is more fiddly as it seems you can't actually expose an array using a get/let you have to have it take an index and expose elements individually.
So at this point I am thinking forget the strongly typed it's not happening, perhaps use a collection?
The FancySock class may have further nested arrays within it. I've read that there's no ByRef for arrays (at least, not completely - I think you can get an array ByRef but not set one?). I am not sure if that would create problems with trying to set it.
But ultimately, I just want to end up with my JSON data represented easily in an OO way, so that in my excel ultimately I can just do
myFancyCat.Name or myFancyCat.Socks.Count or myFancyCat.Socks(1).Colour etc
It seems much harder than it looks to simply deserialise JSON into 'objects' in vba.
Please, try the next way:
Insert a class module, name it FancyCat and copy the next code:
Option Explicit
Private arrL As Object
Public myName As String, myAge As Long
Public Sub Class_Initialize()
Set arrL = CreateObject("System.Collections.ArrayList")
End Sub
Public Property Let Name(strName As String)
myName = strName
End Property
Public Property Let Age(lngAge As String)
myAge = lngAge
End Property
Public Property Let SocksAdd(sMember)
arrL.Add sMember
End Property
Public Property Get Socks() As Variant
Socks = arrL.toarray()
End Property
Use it in the next testing Sub:
Sub testClassDictListArray()
Dim myFancyCat As New FancyCat, myData As Object
Dim arrSocks, sock
Set myData = CreateObject("Scripting.Dictionary") 'this should be the dictionary returned by ParseJSON
myData.Add "Name", "John Doe": myData.Add "Age", 35
myData.Add "Socks", Array("Blue", "White", "Red", "Green", "Yellow")
myFancyCat.Name = myData("Name")
myFancyCat.Age = myData("Age")
For Each sock In myData("Socks")
myFancyCat.SocksAdd = sock
Next sock
arrSocks = myFancyCat.Socks
Debug.Print Join(arrSocks, "|")
End Sub
I am not sure I perfectly understand the scenario you try putting in discussion...
If you want to benefit of instellisense suggestions, I will tell you what references to be added. Even, I will send two pieces of code to automatically add the necessary references (I mean, Scripting.Dictionary and ArrayList`).
Please, test it and send some feedback.
In your class:
Private m_Name As String
Private m_Socks() As String
Public Property Let Name(Name As String)
m_Name = Name
End Property
Public Property Get Name() As String
Name = m_Name
End Property
Public Sub SetSize(Quantity As Long)
ReDim m_Socks(1 To Quantity)
End Sub
Public Property Let Socks(Index As Long, Sock As String)
m_Socks(Index) = Sock
End Property
Public Property Get Socks(Index As Long) As String
Socks = m_Socks(Index)
End Property
In a regular module:
Sub UseFancyCat()
Dim MyFancyCat As FancyCat
Set MyFancyCat = New FancyCat
MyFancyCat.Name = "Fancy Name"
MyFancyCat.SetSize 2
MyFancyCat.Socks(1) = "Sock1"
MyFancyCat.Socks(2) = "Sock2"
Debug.Print MyFancyCat.Name
Debug.Print MyFancyCat.Socks(1)
Debug.Print MyFancyCat.Socks(2)
End Sub
I've created some simple classes in excel and I'm trying to create new objects from these classes. It works fine and let's me create them and I can also access the variables given to the object. I can't see the object in the local window though and I don't really understand why. Is it not created correctly because you are supposed to see your objects there I understand?
Here is the code for the class
Option Explicit
'Teams
Public Name As String
Public Group As String
Public GF As Integer
Public GA As Integer
Public Points As Integer
'Public Players(25) As String
Private Sub class_initialize()
Points = 5
End Sub
and here is the code where I try to create an object
Sub TestTeams()
Dim Madagaskar As Object
Set Madagaskar = New ETeam
MsgBox (Madagaskar.Points)
End Sub
If you put Stop on the line after the MsgBox call and run TestTeams, you will see the object in the locals window.
It will only be there while Madagaskar is in scope and you're in break mode.
Preface
About 10 years ago I started refactoring and improving the ChartSeries class of John Walkenbach. Unfortunately it seems that the original it is not available any more online.
Following the Rubberduck Blog for quite some time now I try to improve my VBA skills. But in the past I only have written -- I guess the experts would call it -- "script-like god-procedures" (because of not knowing better). So I am pretty new to classes and especially interfaces and factories.
Actual Questions
I try to refactor the whole class by dividing it into multiple classes also using interfaces and than also adding unit tests. For just reading the parts of a formula it would be sufficient to get the Series.Formula and then do all the processing. So it would be nice to call the Run sub in the Create function. But everything I tried so far to do so failed. Thus, I currently running Run in all Get properties etc. (and test, if the formula changed and exit Run than. Is this possible and when yes, how?
Second, to add unit tests -- of course using rubberduck for them -- I currently rely on real Charts/ChartObjects. How do I create a stub/mock/fake for a Series? (Sorry, I don't know the correct term.)
And here a simplified version of the code.
Many thanks in advance for any help.
normal module
'#Folder("ChartSeries")
Option Explicit
Public Sub ExampleUsage()
Dim wks As Worksheet
Set wks = ThisWorkbook.Worksheets(1)
Dim crt As ChartObject
Set crt = wks.ChartObjects(1)
Dim srs As Series
Set srs = crt.Chart.SeriesCollection(3)
Dim MySeries As IChartSeries
Set MySeries = ChartSeries.Create(srs)
With MySeries
Debug.Print .XValues.FormulaPart
End With
End Sub
IChartSeries.cls
'#Folder("ChartSeries")
'#Interface
Option Explicit
Public Function IsSeriesAccessible() As Boolean
End Function
Public Property Get FullFormula() As String
End Property
Public Property Get XValues() As ISeriesPart
End Property
'more properties ...
ChartSeries.cls
'#PredeclaredId
'#Exposed
'#Folder("ChartSeries")
Option Explicit
Implements IChartSeries
Private Type TChartSeries
Series As Series
FullSeriesFormula As String
OldFullSeriesFormula As String
IsSeriesAccessible As Boolean
SeriesParts(eElement.[_First] To eElement.[_Last]) As ISeriesPart
End Type
Private This As TChartSeries
Public Function Create(ByVal Value As Series) As IChartSeries
'NOTE: I would like to run the 'Run' sub somewhere here (if possible)
With New ChartSeries
.Series = Value
Set Create = .Self
End With
End Function
Public Property Get Self() As IChartSeries
Set Self = Me
End Property
Friend Property Let Series(ByVal Value As Series)
Set This.Series = Value
End Property
Private Function IChartSeries_IsSeriesAccessible() As Boolean
Call Run
IChartSeries_IsSeriesAccessible = This.IsSeriesAccessible
End Function
Private Property Get IChartSeries_FullFormula() As String
Call Run
IChartSeries_FullFormula = This.FullSeriesFormula
End Property
Private Property Get IChartSeries_XValues() As ISeriesPart
Call Run
Set IChartSeries_XValues = This.SeriesParts(eElement.eXValues)
End Property
'more properties ...
Private Sub Class_Initialize()
With This
Dim Element As eElement
For Element = eElement.[_First] To eElement.[_Last]
Set .SeriesParts(Element) = New SeriesPart
Next
End With
End Sub
Private Sub Class_Terminate()
With This
Dim Element As LongPtr
For Element = eElement.[_First] To eElement.[_Last]
Set .SeriesParts(Element) = Nothing
Next
End With
End Sub
Private Sub Run()
If Not GetFullSeriesFormula Then Exit Sub
If Not HasFormulaChanged Then Exit Sub
Call GetSeriesFormulaParts
End Sub
'(simplified version)
Private Function GetFullSeriesFormula() As Boolean
GetFullSeriesFormula = False
With This
'---
'dummy to make it work
.FullSeriesFormula = _
"=SERIES(Tabelle1!$B$2,Tabelle1!$A$3:$A$5,Tabelle1!$B$3:$B$5,1)"
'---
.OldFullSeriesFormula = .FullSeriesFormula
.FullSeriesFormula = .Series.Formula
End With
GetFullSeriesFormula = True
End Function
Private Function HasFormulaChanged() As Boolean
With This
HasFormulaChanged = (.OldFullSeriesFormula <> .FullSeriesFormula)
End With
End Function
Private Sub GetSeriesFormulaParts()
Dim MySeries As ISeriesFormulaParts
'(simplified version without check for Bubble Chart)
Set MySeries = SeriesFormulaParts.Create( _
This.FullSeriesFormula, _
False _
)
With MySeries
Dim Element As eElement
For Element = eElement.[_First] To eElement.[_Last] - 1
This.SeriesParts(Element).FormulaPart = _
.PartSeriesFormula(Element)
Next
'---
'dummy which normally would be retrieved
'by 'MySeries.PartSeriesFormula(eElement.eXValues)'
This.SeriesParts(eElement.eXValues).FormulaPart = _
"Tabelle1!$A$3:$A$5"
'---
End With
Set MySeries = Nothing
End Sub
'more subs and functions ...
ISeriesPart.cls
'#Folder("ChartSeries")
'#Interface
Option Explicit
Public Enum eEntryType
eNotSet = -1
[_First] = 0
eInaccessible = eEntryType.[_First]
eEmpty
eInteger
eString
eArray
eRange
[_Last] = eEntryType.eRange
End Enum
Public Property Get FormulaPart() As String
End Property
Public Property Let FormulaPart(ByVal Value As String)
End Property
Public Property Get EntryType() As eEntryType
End Property
Public Property Get Range() As Range
End Property
'more properties ...
SeriesPart.cls
'#PredeclaredId
'#Folder("ChartSeries")
'#ModuleDescription("A class to handle each part of the 'Series' string.")
Option Explicit
Implements ISeriesPart
Private Type TSeriesPart
FormulaPart As String
EntryType As eEntryType
Range As Range
RangeString As String
RangeSheet As String
RangeBook As String
RangePath As String
End Type
Private This As TSeriesPart
Private Property Get ISeriesPart_FormulaPart() As String
ISeriesPart_FormulaPart = This.FormulaPart
End Property
Private Property Let ISeriesPart_FormulaPart(ByVal Value As String)
This.FormulaPart = Value
Call Run
End Property
Private Property Get ISeriesPart_EntryType() As eEntryType
ISeriesPart_EntryType = This.EntryType
End Property
Private Property Get ISeriesPart_Range() As Range
With This
If .EntryType = eEntryType.eRange Then
Set ISeriesPart_Range = .Range
Else
' Call RaiseError
End If
End With
End Property
Private Property Set ISeriesPart_Range(ByVal Value As Range)
Set This.Range = Value
End Property
'more properties ...
Private Sub Class_Initialize()
This.EntryType = eEntryType.eNotSet
End Sub
Private Sub Run()
'- set 'EntryType'
'- If it is a range then find the range parts ...
End Sub
'a lot more subs and functions ...
ISeriesParts.cls
'#Folder("ChartSeries")
'#Interface
Option Explicit
Public Enum eElement
[_First] = 1
eName = eElement.[_First]
eXValues
eYValues
ePlotOrder
eBubbleSizes
[_Last] = eElement.eBubbleSizes
End Enum
'#Description("fill me")
Public Property Get PartSeriesFormula(ByVal Element As eElement) As String
End Property
SeriesFormulaParts.cls
'#PredeclaredId
'#Exposed
'#Folder("ChartSeries")
Option Explicit
Implements ISeriesFormulaParts
Private Type TSeriesFormulaParts
FullSeriesFormula As String
IsSeriesInBubbleChart As Boolean
WasRunCalled As Boolean
SeriesFormula As String
RemainingFormulaPart(eElement.[_First] To eElement.[_Last]) As String
PartSeriesFormula(eElement.[_First] To eElement.[_Last]) As String
End Type
Private This As TSeriesFormulaParts
Public Function Create( _
ByVal FullSeriesFormula As String, _
ByVal IsSeriesInBubbleChart As Boolean _
) As ISeriesFormulaParts
'NOTE: I would like to run the 'Run' sub somewhere here (if possible)
With New SeriesFormulaParts
.FullSeriesFormula = FullSeriesFormula
.IsSeriesInBubbleChart = IsSeriesInBubbleChart
Set Create = .Self
End With
End Function
Public Property Get Self() As ISeriesFormulaParts
Set Self = Me
End Property
'#Description("Set the full series formula ('ChartSeries')")
Public Property Let FullSeriesFormula(ByVal Value As String)
This.FullSeriesFormula = Value
End Property
Public Property Let IsSeriesInBubbleChart(ByVal Value As Boolean)
This.IsSeriesInBubbleChart = Value
End Property
Private Property Get ISeriesFormulaParts_PartSeriesFormula(ByVal Element As eElement) As String
'NOTE: Instead of running 'Run' here, it would be better to run it in 'Create'
Call Run
ISeriesFormulaParts_PartSeriesFormula = This.PartSeriesFormula(Element)
End Property
'(replaced with a dummy)
Private Sub Run()
If This.WasRunCalled Then Exit Sub
'extract stuff from
This.WasRunCalled = True
End Sub
'a lot more subs and functions ...
You can already!
Public Function Create(ByVal Value As Series) As IChartSeries
With New ChartSeries <~ With block variable has access to members of the ChartSeries class
.Series = Value
Set Create = .Self
End With
End Function
...only, like the .Series and .Self properties, it has to be a Public member of the ChartSeries interface/class (the line is blurry in VBA, since every class has a default interface / is also an interface).
Idiomatic Object Assignment
A note about this property:
Friend Property Let Series(ByVal Value As Series)
Set This.Series = Value
End Property
Using a Property Let member to Set an object reference will work - but it isn't idiomatic VBA code anymore, as you can see in the .Create function:
.Series = Value
If we read this line without knowing about the nature of the property, this looks like any other value assignment. Only problem is, we're not assigning a value, but a reference - and reference assignments in VBA are normally made using a Set keyword. If we change the Let for a Set in the Series property definition, we would have to do this:
Set .Series = Value
And that would look much more readily like the reference assignment it is! Without it, there appears to be implicit let-coercion happening, and that makes it ambiguous code: VBA requires a Set keyword for reference assignments, because any given object can have a paraterless default property (e.g. how foo = Range("A1") implicitly assigns foo to the Value of the Range).
Caching & Responsibilities
Now, back to the Run method - if it's made Public on the ChartSeries class, but not exposed on the implemented IChartSeries interface, then it's a member that can only be invoked from 1) the ChartSeries default instance, or 2) any object variable that has a ChartSeries declared type. And since our "client code" is working off IChartSeries, we can guard against 1 and shrug off 2.
Note that the Call keyword is superfluous, and the Run method is really just pulling metadata from the encapsulated Series object, and caching it at instance level - I'd give it a name that sounds more like "refresh cached properties" than "run something".
Your hunch is a good one: Property Get should be a simple return function, without any side-effects. Invoking a method that scans an object and resets instance state in a Property Get accessor makes it side-effecting, which is a design smell - in theory.
If Run is invoked immediately after creation before the Create function returns the instance, then this Run method boils down to "parse the series and cache some metadata I'll reuse later", and there's nothing wrong with that: invoke it from Create, and remove it from the Property Get accessors.
The result is an object whose state is read-only and more robustly defined; the counterpart of that is that you now have an object whose state might be out of sync with the actual Excel Series object on the worksheet: if code (or the user) tweaks the Series object after the IChartSeries is initialized, the object and its state is stale.
One solution is to go out of your way to identify when a series is stale and make sure you keep the cache up-to-date.
Another solution would be to remove the problem altogether by no longer caching the state - that would mean one of two things:
Generating the object graph once on creation, effectively moving the caching responsibility to the caller: calling code gets a read-only "snapshot" to work with.
Generating a new object graph out of the series metadata, every time the calling code needs it: effectively, it moves the caching responsibility to the caller, which isn't a bad idea at all.
Making things read-only removes a lot of complexity! I'd go with the first option.
Overall, the code appears nice & clean (although it's unclear how much was scrubbed for this post) and you appear to have understood the factory method pattern leveraging the default instance and exposing a façade interface - kudos! The naming is overall pretty good (although "Run" sticks out IMO), and the objects look like they each have a clear, defined purpose. Good job!
Unit Testing
I currently rely on real Charts/ChartObjects. How do I create a stub/mock/fake for a Series? (Sorry, I don't know the correct term.)
Currently, you can't. When if/when this PR gets merged, you'll be able to mock Excel's interfaces (and much, much more) and write tests against your classes that inject a mock Excel.Series object that you can configure for your tests' purposes... but until then, this is where the wall is.
In the mean time, the best you can do is wrap it with your own interface, and stub it. In other words, wherever there's a seam between your code and Excel's object model, we slip an interface between the two: instead of taking in a Excel.Series object, you'd be taking in some ISeriesWrapper, and then the real code would be using an ExcelSeriesWrapper that works off an Excel.Series, and the test code might be using a StubSeriesWrapper whose properties return either hard-coded values, or values configured by tests: the code that works at the seam between the Excel library and your project, can't be tested - and we woulnd't want to anyway, because then we'd be testing Excel, not our own code.
You can see this in action in the example code for the next upcoming RD News article here; that article will discuss exactly this, using ADODB connections. The principle is the same: none of the 94 unit tests in that project ever open any actual connection, and yet with dependency injection and wrapper interfaces we're able to test every single bit of functionality, from opening a database connection to committing a transaction... without ever hitting an actual database.
I'm losing quite some time copy-pasting identical properties and methods in various vba custom object I'm building. How do I create an custom-object hierarchy in VBA so one object and inherit properties and methods from others.
In python I would prob write something like:
Class Car(Object)
whatever
Class SlowCar(Car)
inherit whatever
Class FastCar(Car)
inherit whatever
tks in advance.
If i understand what you're saying, this can be done via the Class Module.
From the VBA Editor, select Insert > Class Module
Change the name of the class Module to whatever you want (Car for
example) via the Properties Window (press F4 to make it appear if it
does not already)
Now that you've created your class module you can define its variables and/or properties. The example below would go into your Car Class Module creates a object that holds a car name and a speed
Private carName As String
Private carSpeed As Integer
' Car Name
Public Property Get Name() As String
Name = carName
End Property
Public Property Let Name(result As String)
carName = result
End Property
' Car Speed
Public Property Get Speed() As Integer
Speed = carSpeed
End Property
Public Property Let Speed(result As Integer)
carSpeed = result
End Property
Then from your Module, you can do the following
Sub CreateMyCars()
Dim slowCar as Car
Dim fastCar as Car
Set slowCar = New Car
Set fastCar = New Car
slowCar.Name = "GoKart"
slowCar.Speed = 35
fastCar.Name = "Ferarri"
fastCar.Speed = 185
End Sub
VBA supports inheritance through the use of Interfaces, but they only "inherit" the signature of methods, not the implementation.
A way to reuse an object implementation would be through composition.
Class Car(Object)
whatever
Class SlowCar(Car)
Implements Car
private mCar as Car
Private Sub Class_Initialize
set mCar = new Car
End Sub
Private Sub Car_whatever
Call mCar.whatever
End Sub
And same for FastCar.
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