Solved Class Properties Assigned From Procedures (3 Viewers)

[dalski]

I have some Properties (around 30; most are typical assignment format). Some values are assigned by procedures/ routines inside the Property/ or called. I'm probably going to get told off but these are quite intrinsic values to the class object. I would prefer to call a function to keep the Properties section clear as it's getting quite big & a little obfuscated but I can't figure out what's up.
I intermittently keep generating the error below; despite trying to follow guidance:

• Returning correct data-types
• Query returns a single value
• Having the NewValue argument in the Let procedure... ensuring there is one more parameter than in the Get procedure
• _________________________________________________________________________________________________________________________________
• Additionally tried separating simplifying & just calling a function to return result
• Have similar Property - works fine
• Aware that I don't need to open rs type as Snapshot as a union query is read-only; looking for the slight performance gain (pedantic here I think)

Public Property Let PropName(NewValue As Long)
  Dim rs As DAO.Recordset
  Set rs = CurrentDb.OpenRecordset("UnionQueryName", dbOpenSnapshot, dbSeeChanges)
  NewValue = rs!FieldName
  mPropName = NewValue
  'mPropName = rs!FieldName  -  FAILS ALSO
  rs.Close
End Property

Public Property Get PropName()
  PropName= mPropName
End Property

 

[arnelgp]

I would change it to a Public Sub rather than a Let Property.
since you are assigning the value directly through query.
how do you supposed to assign Value from your code?

Public Sub AssignPropName()
  Dim rs As DAO.Recordset
  Set rs = CurrentDb.OpenRecordset("UnionQueryName", dbOpenSnapshot, dbSeeChanges)
  mPropName = rs!FieldName & ""
  rs.Close: Set rs = Nothing
End Sub

 

[dalski]

Thanks, yeah I had it as a sub/ function but seemed more intrinsic & seems clearer as a property.

"how do you supposed to assign Value from..." unsure what you mean here. Originally I had it as a function, would call it where needed & store it in the module var. But thought between calls hypothetically if viewing a different record (which the class is linked to) it would be misleading to have a value in the property so would set it to 0 between records & only populate it when required.

Yeah as I'm typing I see your logic. So are Properties only for real basic assignment?
What I didn't like when using it as a function is for any real implementation another temporary variable needs to be created to store the result of the function if using >1 place. The alternative is as a sub & populating the module level variable mPropName, but then the problem of a misleading value from the selection between values. Which I could wipe the module var with a property setting of 0 on each current record selection.

 

[arnelgp]

Yeah as I'm typing I see your logic. So are Properties only for real basic assignment?

 

[cheekybuddha]

Don't you have to declare the property type in the signature?

Public Property Get PropName() As Long

 

[dalski]

Thanks cheekybuddha, you're dead right. I'm perplexed as i have a near identical property that's working fine. Just can't spot what the issue is. I'm not enjoying superflating the Properties with methods & may prefer a call, but in the interest of trying to learn; can't help but play around.

 

[arnelgp]

Don't you have to declare the property type in the signature?

i think you only need to do that on another Class that you want to Implement

 

[arnelgp]

I intermittently keep generating the error below; despite trying to follow guidance:

• Returning correct data-types

 

[dalski]

i think you only need to do that on another Class that you want to Implement

No @cheekybuddha solved it, that was the issue here. Maybe when there's more going on than a basic assignment. I've gotten away with just using a basic Get most places but he's right.

 

[arnelgp]

he's dead right alright and your all wrong on your Let Property.

 

[cheekybuddha]

You just have to match to the input type to the return type:
Eg

Public Property Let PropName(NewValue As Long)
  ' ...
End Property

Public Property Get PropName() As Long
  ' ...
End Property

' OR:

Public Property Let PropName(NewValue)  ' implicit Variant
  ' ...
End Property

Public Property Get PropName()
  ' ...
End Property

Doing the database lookup in the Let() is totally unnecessary - if you *must* do it then just do it in the Get() and don't have a Let() (ie read-only property)

Otherwise, cache the result, so you don't hit the db with a lookup each time you call (Get()) the property.

But much better to leave the Let/Get's in their simple form and load all the properties from a single recordset lookup in your class initialisation.

 

[KitaYama]

I was waiting for someone to ask/explain why the data type is different:

Public Property Let PropName(NewValue As Long)
  .......
  NewValue = rs!FieldName

It seems that FieldName is a string.

 

[dalski]

Thanks all, appreciate that guidance that's not how to use properties.

I was waiting for someone to ask/explain why the data type is different:

I don't think that's correct, that's been taken out of context; you've removed the apostrophe & also removed FAILS ALSO. Which was to show I had experimented so this line is not even in execution. You have no way of knowing what that datatype is but you can see I've defined it as Long; which it was. I thought I'd leave it there in case someone was to mention to watch out for implicit type conversions which I don't know whether or not that would default because of returning an object type of recordset; opposed to a Long as explicitly defined in the Let parameter.

Turns out I'm using Properties in a despicable way & not to be done like that.