How to get Object property using EVAL()?

[Genki]

Can you figure out how to do this in Access2002/VBA?

I want to get the value of an object property. The trick is that the name of the property to retrieve is stored in a table.

Here's how I've set it up:

I have a class module "objPerson" which has a property "FirstName".
This works:

objPerson.FirstName = "John Smith"
strFirstName = objPerson.FirstName

and it will correctly set
strFirstName = "John Smith"

So far, so good, right?

Next, in "MyTable" I have a field "MyField" which contains the text string "objPerson.FirstName"

I want to get the value of the item specified by the string in MyField. In other words, I want the program to determine the value of whatever object property that I have stored in MyField. In this case, I have opened the object objPerson and I want the program to give me the value of "objPerson.FirstName".

I've tried using Eval(), but so far it doesn't work:

strFirstName = Eval(rst.Fields("MyField"))

The result is: "Error 2482: Microsoft Access can't find the name 'objTenant' you entered in the expression."

MY OBJECTIVE

My objective is to do string replacement where the REPLACEMENT text is set in a table, like this:

In "MyTable":
 
Field:KEY                     Field:REPLACE_WITH
-------------------------     -------------------------------------
Tenant.FirstName              objTenant.FirstName
Owner.FirstName               objOwner.FirstName
Balance                       objInvoice.BalanceAmount
(etc...)
 
strMsg = "Hello [Tenant.FirstName]. Your invoice balance is [Invoice.Balance]"
strMsg = MySpecializedReplacementFunction(strMsg)
strMsg: "Hello John. Your invoice balance is $10"

[willakawill]

Hi. What I would do is use the value in the table to activate a section of code in a Select Case statement;

Select Case rs.Fields("Field1")
   Case "objPerson.FirstName"
      strText = objPerson.FirstName
 
   Case "something else"
      'peform whatever it says here
End Select
 

Hope this helps

[Genki]

Thank you, Willakawill. That is a workable alternative.

The only disadvantage is that the fields would have to be hardcoded in the SELECT-CASE statement. Ideally, updating the list of string Keys and the Replacement text would be maintainable via a table.

[nico5038]

For just the property this should work:

dim arr

arr = split(rs!Replace_with,".")

select case arr(0)
Case "objTenant"
strX = objTenant.properties(arr(1))
Case .... etc ...

The Split will fill an array (zero based!) with the two parts and arr(0) will hold the object and arr(1) the property.

Getting the idea ?

Nic;o)

[Genki]

Hi nico5038,

I really like your idea. It allows the substitutions to be solved dynamically and that's important to me.

[Genki]

Nico,

I've added the code but it doesn't like the .Properties in objTenant.Properties. I get an error:

Dim objTenant As pm_Tenant
Set objTenant = New pm_Tenant
objTenant.Load (TenantID)
 
Debug.Print "name1=" & objTenant.FullName
' ^ up to here it works. It correctly displays: Name1=Joe Smith
 
' The following lines return an error:  "Compile error: Method or data member not found"
Debug.Print "name2=" & objTenant.Properties("FullName")   
Debug.Print "name3=" & objTenant.Properties!FullName
 

Of course, I'm using the hard-coded "FullName" just to test it. Once it's working, I'll change to using your suggestion, .Properties(arr(1))

[nico5038]

Hmm, strange. Are you sure the properties have been defined correctly ?

To test use:

objTenant.properties.count

This will get the number of properties and check the available by using:

objTenant.properties(0).Name

You can see the property names there are.

Nic;o)

[Genki]

I tried and both statements give the error "method or data member not found". For some reason, my Access VBA doesn't understand ".properties":

objTenant.properties.count
objTenant.properties(0).FirstName

Maybe a reference needs to be set in Tools > References?
Am I setting the properties correctly? As you can see below, I have "Property Let" and "Property Get" procedures and they are working just fine. If I type "? objTenant.Name" I get the correct result.

Public Property Get FirstName() As String
    FirstName = mstrFirstName
End Property
 
Public Property Let FirstName(NewValue As String)
    mstrFirstName = NewValue
End Property

[nico5038]

I'm startled, but have asked another expert to join.

Nic;o)

[willakawill]

Public Property Get FirstName() As String
    FirstName = mstrFirstName
End Property
 
Public Property Let FirstName(NewValue As String)
    mstrFirstName = NewValue
End Property

OK here is another way you can do this using vb6 and the following class module. I have tested this and it works :)

'MyDog.cls class module
'local variable(s) to hold property value(s)
Private mvarDogName As String 'local copy
Private mvarTailWags As Integer 'local copy
Public Sub FeedDog(Optional NumCookies As Integer = 1)
    mvarTailWags = mvarTailWags + Abs(NumCookies * 5)
End Sub
 
Public Property Let TailWags(ByVal vData As Integer)
'used when assigning a value to the property, on the left side of an assignment.
'Syntax: X.TailWags = 5
    mvarTailWags = vData
End Property
 
 
Public Property Get TailWags() As Integer
'used when retrieving value of a property, on the right side of an assignment.
'Syntax: Debug.Print X.TailWags
    TailWags = mvarTailWags
End Property
 
 
 
Public Property Let DogName(ByVal vData As String)
'used when assigning a value to the property, on the left side of an assignment.
'Syntax: X.DogName = 5
    mvarDogName = vData
End Property
 
 
Public Property Get DogName() As String
'used when retrieving value of a property, on the right side of an assignment.
'Syntax: Debug.Print X.DogName
    DogName = mvarDogName
End Property
 
Public Property Get NewValue(stValue As String) As String
    Select Case stValue
        Case "DogName"
            NewValue = mvarDogName
        Case "TailWags"
            NewValue = CStr(mvarTailWags)
    End Select
End Property
 

then in a form module:

Private Sub cmdFeedTheDog_Click()
    Dim MyNewDog As MyDog
    Set MyNewDog = New MyDog
    MyNewDog.DogName = "Fido"
    MyNewDog.FeedDog 5
    MsgBox CInt(MyNewDog.NewValue("TailWags"))
End Sub
 

[pks00]

This code

Dim objTenant As pm_Tenant
Set objTenant = New pm_Tenant


is this referring to pm_Tenant as a class object?
And FullName is a variable inside your class?

If that is the case, then u cant access it using Properties as this is not a valid method for classes. U need to write public functions or create the public property functions like willakawill has shown/

or am I thinking this wrong.

[willakawill]

This code

Dim objTenant As pm_Tenant
Set objTenant = New pm_Tenant


is this referring to pm_Tenant as a class object?
And FullName is a variable inside your class?

If that is the case, then u cant access it using Properties as this is not a valid method for classes. U need to write public functions or create the public property functions like willakawill has shown/

or am I thinking this wrong.

You are right. This is a confusion between user defined classes and inherent system objects

[Genki]

Yes, pm_Tenant is a class module and .FullName is a property (a variable) of the class.

I think you are saying to create a function within the class module that returns the value, rather than using a property to return the value.

Thank you for your replies... I'll digest your example and see if it works for me.

[willakawill]

Yes, pm_Tenant is a class module and .FullName is a property (a variable) of the class.

I think you are saying to create a function within the class module that returns the value, rather than using a property to return the value.

Thank you for your replies... I'll digest your example and see if it works for me.

Property and variable are not interchangeable. They are not the same thing