Instantiating variables

[tiredofit]

If I have a class with a property, I must instantiate it before using it.

So either:

Dim UseClass As MyClass
Set UseClass = New MyClass

Msgbox UseClass.Age = 10

or

Dim UseClass As New MyClass

Msgbox UseClass.Age = 10

I don't understand why the following code works.

This is in a class called Holiday:

Option Explicit

Public CountryName As String
Public ResortName As String
Public DaysLength As Integer
Public TravelMethod As String
Public Price As Currency
Public HolidayId As String

This is in another class called Holdiays:

Option Explicit

Private p_Holidays As Collection
Private Sub Class_Initialize()
 
Set p_Holidays = New Collection

End Sub

Sub Add(ThisHoliday As Holiday, HolidayId As String)

    p_Holidays.Add Item:=ThisHoliday, key:=HolidayId

End Sub

Public Property Get Item(HolidayId As Variant) As Holiday

    Set Item = p_Holidays(HolidayId)

End Property

Public Sub Remove(HolidayId As Variant)

    p_Holidays.Remove (HolidayId)

End Sub

Public Property Get Count() As Long

    Count = p_Holidays.Count

End Property

This is in a standard module:

Option Explicit

Dim SummerHolidays As Holidays

Sub DemonstrateClass()

    ReadHolidays

    WriteHolidays

End Sub

Sub ReadHolidays()
   
    Dim EachCell As Range
    Dim h As Holiday

    Set SummerHolidays = New Holidays

    Range("A4").Select
    Range(ActiveCell, ActiveCell.End(xlDown)).Select

    For Each EachCell In Selection

        Set h = New Holiday

        h.CountryName = EachCell.Value
        h.ResortName = EachCell.Offset(0, 1).Value
        h.DaysLength = EachCell.Offset(0, 2).Value
        h.TravelMethod = EachCell.Offset(0, 3).Value
        h.Price = EachCell.Offset(0, 4).Value
        h.HolidayId = EachCell.Offset(0, 5).Value

        SummerHolidays.Add h, h.HolidayId

        Set h = Nothing

    Next EachCell

End Sub

Sub WriteHolidays()

    Dim h As Holiday
    Dim HolidayNumber As Integer

    For HolidayNumber = 1 To SummerHolidays.Count

        '*************************************************
        Set h = SummerHolidays.Item(HolidayNumber)
        '*************************************************

        Debug.Print "Holiday " & h.HolidayId & " to " & h.ResortName & " in " & h.CountryName & " by " & h.TravelMethod & _
        " lasts for " & h.DaysLength & " days and costs " & Format(h.Price, "?#,##0.00")

    Next HolidayNumber

End Sub

In Sub WriteHolidays, we have:

Dim h As Holiday

but it seems it has not been instantiated because I don't see:

Set h = New Holiday

Instead, this line follows:

Set h = SummerHolidays.Item(HolidayNumber)

Can someone please explain why the variable h looks like it has not been instantiated, yet can still be used?

Thanks

 

[mikerickson]

h is declared to be a Holiday, but we don't know which Holiday yet.

Set h = New Holiday

says that h is a brand new instance of a Holiday

Set h = SummerHolidays.Item(HolidayNumber)

says that h is the an already existing instance of Holiday.

One doesn't instantiate variables, one instantiates objects. And then sets variables to that object.
The SummerHolidays.Item(HolidayNumber) was instantiated in the ReadHolidays sub (and stored in a collection)

This is where one has to be mindful of the difference between an object and a variable that refers to that object.

 

[tiredofit]

h is declared to be a Holiday, but we don't know which Holiday yet.

Set h = New Holiday

says that h is a brand new instance of a Holiday

Set h = SummerHolidays.Item(HolidayNumber)

says that h is the an already existing instance of Holiday.

One doesn't instantiate variables, one instantiates objects. And then sets variables to that object.
The SummerHolidays.Item(HolidayNumber) was instantiated in the ReadHolidays sub (and stored in a collection)

This is where one has to be mindful of the difference between an object and a variable that refers to that object.

Thanks for your explanation.