Putting dictionaries into classes

Question

I was given an answer on how to make a general class module: Class "let" stuck in infinite loop

I'm trying to apply this to dictionaries inside my classes.

My class module:

Option Explicit

Private Type categories
    Temp As scripting.Dictionary
    Humid As scripting.Dictionary
    Wind As scripting.Dictionary
End Type

Private this As categories

Public Sub Initialize()
    Set this.Temp = New scripting.Dictionary
    Set this.Humid = New scripting.Dictionary
    Set this.Wind = New scripting.Dictionary
End Sub

Public Property Get Temp(ByVal HourIndex As Long) As Double
    Temp = this.Temp(HourIndex)
End Property

Public Property Let Temp(ByVal HourIndex As Long, ByVal Value As Double)
    this.Temp(HourIndex) = Value
End Property

Public Property Get Humid(ByVal HourIndex As Long) As Double
    Humid = this.Humid(HourIndex)
End Property

Public Property Let Humid(ByVal HourIndex As Long, ByVal Value As Double)
    this.Humid(HourIndex) = Value
End Property

Public Property Get Wind(ByVal HourIndex As Long) As Double
    Wind = this.Wind(HourIndex)
End Property

Public Property Let Wind(ByVal HourIndex As Long, ByVal Value As Double)
    this.Wind(HourIndex) = Value
End Property

I tried to test this in the immediate window with set tester = new WeatherData (the name of the module) and Initialize. That did not work.

I then modified Initialize:

Public Sub Initialize(ByVal variable As categories)
    Set variable.Temp = New scripting.Dictionary
    Set variable.Humid = New scripting.Dictionary
    Set variable.Wind = New scripting.Dictionary
End Sub

and entered Initialize tester, but this did not work either ("Compile Error: Sub or Function not defined").

How do I put three dictionaries in a class module?

The following doesn't solve the problem, but it did skirt around it to the point that I don't have to acknowledge it:

Option Explicit

Private Type categories
    Temp(23) As Double
    Humid(23) As Double
    wind(23) As Double
End Type

Private this As categories

Public Property Get Temp(ByVal HourIndex As Long) As Double
    Temp = this.Temp(HourIndex)
End Property

Public Property Let Temp(ByVal HourIndex As Long, ByVal Value As Double)
    this.Temp(HourIndex) = Value
End Property

Public Property Get Humid(ByVal HourIndex As Long) As Double
    Humid = this.Humid(HourIndex)
End Property

Public Property Let Humid(ByVal HourIndex As Long, ByVal Value As Double)
    this.Humid(HourIndex) = Value
End Property

Public Property Get wind(ByVal HourIndex As Long) As Double
    wind = this.WindChill(HourIndex)
End Property

Public Property Let wind(ByVal HourIndex As Long, ByVal Value As Double)
    this.wind(HourIndex) = Value
End Property

tl;dr: make arrays instead of dictionaries, and cut out initialize entirely. Your "keys" have no choice but to be numbers, but it works. I would be interested in knowing an actual solution, but the specific issue is solved.

Answer 1

Seems you want to implement an indexed property.

Simplified to a bare minimum:

Option Explicit
Private values As Scripting.Dictionary

Private Sub Class_Initialize()
    Set values = New Scripting.Dictionary
End Sub

Public Property Get Something(ByVal key As String) As Double
    Something = values(key)
End Property

Public Property Let Something(ByVal key As String, ByVal value As Double)
    values(key) = value
End Property

You keep the dictionaries safely encapsulated as an implementation detail of your class (external code cannot set them to Nothing, for example), and expose an indexed Get+Let property for each encapsulated dictionary, that takes the index (/key) as a parameter.

In the case of your WeatherData class, this means you can populate the data like this:

Set data = New WeatherData
With data
    .Temp("day 1") = 76
    .Temp("day 2") = 78
    .Humid("day 1") = 0.55
    .Humid("day 2") = 0.61
    .Wind("day 1") = 0.92
    .Wind("day 2") = 1.27
End With

And then retrieve the temperature of "day 1" with data.Temp("day 1").

As for your initializer method, it needed to be called from an instance of the class - being an instance method.

So instead of Initialize tester you should have done tester.Initialize.

Whether you make the internal encapsulated storage an array, a Collection or a Dictionary makes no difference to the calling code - it's an encapsulated implementation detail: your class could just as well store the data in .csv files or into a database if it wanted.