VBA - Dictionary search - type mismatch - excel

Question

So I'm learning how to use Dictionaries but I have encountered a type problem. In the code below I get an error.
Type mismatch
Each time I try to call If Not target.SearchItem(sKey) Is Nothing Then. I want it to return a object then if it isn't Nothing I can convert it back to long.
For Each target In dList.getArray
For Each key In aList.getArray(1).getKeys
sKey = CStr(key)
'Error occurs here - as Type mismatch
If Not target.SearchItem(sKey) Is Nothing Then
cData.setData(sKey) = CLng(target.SearchItem(sKey))
target.removeData = sKey
Else
'if value doesn't exists it will just be 0
cData.setData(sKey) = 0
End If
Next key
Next target
data is my dictionary that is in a separate class:
Property Get SearchItem(name As String) As Variant
If data.exists(name) Then
'becomes a Variant/Integer - data(name) is a Variant/long
Set SearchItem = CVar(data(name))
Else
'Should return Nothing if item doesnt exist
Set SearchItem = Nothing
End If
End Property
Update: To explain the problem I bit more. Even though I return it as a variant it will still be partly Integer and therefor If Not target.SearchItem(sKey) Is Nothing Then will return mismatch as it needs an object and VBA doesn't read is as a variant or something. Is there anything like Nothing, null or equally that works for a long? That would solve the problem.
This code below returns a long as I want it to, but I can't use -99 as it would corrupt the data analyse. It needs to be something that isn't a value
Property Get SearchItem(name As String)
If data.exists(name) Then
SearchItem = data(name)
Else
'SearchItem = Nothing
SearchItem = -99
End If
End Property

Answer 1

If Not target.SearchItem(sKey) Is Nothing Then
This implies that the stored item is an Object
cData.setData(sKey) = CLng(target.SearchItem(sKey))
The only way that this line will work on an Object is that the Object has a default value that can be converted to long. If the Object's default value is returning a value that can be converted to long.
Does Clng(Object) work on the actual Object that is being stored in the Dictionary?
If you are storing mixed data type then SearchItem check if the return data is an Object.
Property Get SearchItem(name As String) As Variant
If isObject(data(name)) Then
Set SearchItem = data(name)
Else
SearchItem = data(name)
End If
End Property
I would not convert the datatype in this method. I would instead create one or more separate methods or convert the data type at the point of use.
Function getTypedItem(Key as Variant, DataType as VbVarType) as Variant
IsNumeric(Obj)
Since you are using actual Keys of the Dictionary we know that it will return something and there is not a need for .Exists in this context. What you will need to do is test if it is returning an Object before you test whether the Object Is Nothing.
If IsObject(Target.SearchItem(sKey)) Then
If IsNumeric(Target.SearchItem(sKey)) Then
cData.setData(sKey) = CLng(Target.SearchItem(sKey))
End If
ElseIf IsNumeric(Target.SearchItem(sKey)) Then
cData.setData(sKey) = CLng(Target.SearchItem(sKey))
End If

Answer 2

I don't think you can use Set to assign an integer, so the property will fail when the dictionary item is an Integer. Perhaps use:
Property Get SearchItem(name As String) As Variant
If data.exists(name) Then
'becomes a Variant/Integer - data(name) is a Variant/long
SearchItem = data(name)
...

Answer 3

Unfortunately, VBA does not have nullable primitive types such as a nullable Long. A usual workaround is to use a Variant, which can be assigned the value of Empty and which can also hold a Long natively.
I would rewrite your property as follows:
Property Get SearchItem(name As String) As Variant
If Data.exists(name) Then
SearchItem = Data(name)
Else
SearchItem = Empty
End If
End Property
And the test for empty would be:
If Not IsEmpty(target.SearchItem(sKey)) Then ...