Custom Classes

[Albert D. Kallal]

Re: Custom Classes

I give some thoughts and helpfull advice here:


Using Class objects with ms-access.
By Albert D. Kallal
Tuesday, September 16, 2003

Why would I want to use a class object in ms-access?

http://www.members.shaw.ca/AlbertKallal/Articles/WhyClass.html

--
Albert D. Kallal (Access MVP)
Edmonton, Alberta Canada
pleaseNOOSpamKa llal@msn.com

[Keith Wilby]

Re: Custom Classes

"Albert D. Kallal" <PleaseNOOOsPAM mkallal@msn.com wrote in message
news:GkHbh.3984 09$5R2.297739@p d7urf3no...

>I give some thoughts and helpfull advice here:
>
>
Using Class objects with ms-access.
By Albert D. Kallal
Tuesday, September 16, 2003
>
Why would I want to use a class object in ms-access?
>
http://www.members.shaw.ca/AlbertKal.../WhyClass.html

Thank you Albert, I will read that now.

[Keith Wilby]

Re: Custom Classes

"jlepack" <jlepack@gmail. comwrote in message
news:1164905447 .476289.149010@ l39g2000cwd.goo glegroups.com.. .

Keith,
>
Your problem here is that oyu have followed sound programming
principles. You have created your variables within your class as
Private. Therefore, only methods and functions within your class can
access them, same as a private variable anywhere else for that matter.
>
>
As Gord correctly noted, these Get and Let methods can be accessed
publicly and therefore will allow non-local functions and procedures
that have an instance of your class to modify/view those values.

Duly noted, thanks.

>
PS. You took the "unintersti ng path" and chose the employee and not
the slot machine ;)

That's the kinda guy I am ;)

>
Cheers,
Jason Lepack

[Keith Wilby]

Re: Custom Classes

"Albert D. Kallal" <PleaseNOOOsPAM mkallal@msn.com wrote in message
news:GkHbh.3984 09$5R2.297739@p d7urf3no...

>I give some thoughts and helpfull advice here:
>
>
Using Class objects with ms-access.
By Albert D. Kallal
Tuesday, September 16, 2003
>
Why would I want to use a class object in ms-access?
>
http://www.members.shaw.ca/AlbertKal.../WhyClass.html

Just a quick question Albert.

"when I create and set the myTour = "tour id", then all of the recordsets
for bus company, hotels, rates etc gets loaded into the object."

Could you just expand a little on this please? How does the data get
loaded, do you open a recordset in a subroutine? Still missing the point
here I think!

Thanks.

Keith.

[Gord]

Re: Custom Classes


Keith Wilby wrote:

"Albert D. Kallal" <PleaseNOOOsPAM mkallal@msn.com wrote in message
news:GkHbh.3984 09$5R2.297739@p d7urf3no...

I give some thoughts and helpfull advice here:


Using Class objects with ms-access.
By Albert D. Kallal
Tuesday, September 16, 2003

Why would I want to use a class object in ms-access?

http://www.members.shaw.ca/AlbertKal.../WhyClass.html

>
Just a quick question Albert.
>
"when I create and set the myTour = "tour id", then all of the recordsets
for bus company, hotels, rates etc gets loaded into the object."
>
Could you just expand a little on this please? How does the data get
loaded, do you open a recordset in a subroutine? Still missing the point
here I think!
>
Thanks.
>
Keith.

Hi, Keith.

Here is a simple example of what I *think* Albert is driving at. Notice
that the "Property Let "Salary_Gra de" not only saves the Salary_Grade
you pass it, as in...

objEmployee.Sal ary_Grade = 3

....but it also looks up the corresponding Annual_Salary and saves that
as well, so you can retrieve it via...

objEmployee.Ann ual_Salary

....without doing the lookup yourself.


'-----class module code follows-----

Option Compare Database
Option Explicit

Private mstrLastName As String
Private mintSalary_Grad e As Integer
Private mcurAnnual_Sala ry As Currency

Public Property Get LastName()
' return property value
LastName = mstrLastName
End Property

Public Property Let LastName(ByVal vNewValue As Variant)
' store property value
mstrLastName = vNewValue
End Property

Public Property Get Salary_Grade() As Variant
' return property value
Salary_Grade = mintSalary_Grad e
End Property

Public Property Let Salary_Grade(By Val vNewValue As Variant)
' store property value...
mintSalary_Grad e = vNewValue
' ... and look up annual salary from reference table
mcurAnnual_Sala ry = _
DLookup("Annual _Salary", "Salaries", "Salary_Gra de=" &
mintSalary_Grad e)
End Property

Public Property Get Annual_Salary() As Variant
' return property value
Annual_Salary = mcurAnnual_Sala ry
End Property

[Albert D. Kallal]

Re: Custom Classes

>

"when I create and set the myTour = "tour id", then all of the recordsets
for bus company, hotels, rates etc gets loaded into the object."
>
Could you just expand a little on this please? How does the data get
loaded, do you open a recordset in a subroutine? Still missing the point
here I think!

Yes, in code I could go

dim tour1 as new clsrides
dim tour2 as new clsRides

tour1.TourID = 123 ' load tour 123
tour2.TourID = 34 'load tour 34

At this point, I have TWO tours loaded in ram, and thus go

msgbox "hotel for tour 123 is " & Tour1.HotelName

msgbox "hotel for tour 34 is" & Tour2.HotelName

So, note how the above was VERY little coding, and I can have TWO tours in
memory at the SAME time. And, even if I just need one in code...it is still
much easer then a bunch of subroutines and global variables that would trip
over them selves....

The class object is over 600 lines of code in total.....

Additional properties of the class object are outlined here:

http://www.members.shaw.ca/AlbertKallal/Articles/PickSql/Appendex4.html

The left side does NOT display all properties, but gives you an idea.....


the actual code in the class object for TourID is:

Public Property Let TourId(LoadID As Long)

' Loads/setsup the tour object (pricing etc..)
' DO NOT load if id is same as passed....

Dim myDB As Database
Dim qryBusList As QueryDef

Set myDB = DBEngine(0)(0)

If m_TourId <0 Then
' tour is loaded, check for same tour...
If m_TourId = LoadID Then

' tour already loaded...don't re-load
Exit Property

End If
End If

m_TourId = LoadID

' loads the load rates....

Set m_rstTour = myDB.OpenRecord set("select * from tbltours where id = " &
m_TourId)

With m_rstTour
If .RecordCount 0 Then

m_FromDate = !FromDate
m_Todate = !ToDate
m_HotelId = !Hotel
m_dtDepositDue = m_FromDate - !DaysDue

' load up hotel informaton
Set m_rstHotel = myDB.OpenRecord set("select * from tblHotels where
id = " & m_rstTour!Hotel )

' load up buses attachted to this tour
Set qryBusList = myDB.QueryDefs( "qryTourBusList B")
qryBusList.Para meters(0) = m_TourId
Set m_rstBusList = qryBusList.Open Recordset

' load up seasonal pricing talbes
Call TLoadRates

' set tax tax.
If m_rstTour!NoGst = True Then
m_GstRate = 0
Else
m_GstRate = gblGst(m_FromDa te)
m_PstRate = gblPst(m_FromDa te)
End If

Else
m_TourId = 0
End If
End With

End Property



--
Albert D. Kallal (Access MVP)
Edmonton, Alberta Canada
pleaseNOOSpamKa llal@msn.com

[Albert D. Kallal]

Re: Custom Classes

By the way, that appendix link where I outline that access class object is

is part of larger article here:

http://www.members.shaw.ca/AlbertKallal/Articles/fog0000000003.html

In that article, I explain why I used class objects in ms-access....

--
Albert D. Kallal (Access MVP)
Edmonton, Alberta Canada
pleaseNOOSpamKa llal@msn.com

[Keith Wilby]

Re: Custom Classes

"Albert D. Kallal" <PleaseNOOOsPAM mkallal@msn.com wrote in message
news:%Ooch.4118 71$R63.320926@p d7urf1no...

By the way, that appendix link where I outline that access class object is
>
is part of larger article here:
>

http://www.members.shaw.ca/AlbertKallal/Articles/fog0000000003.html

>
In that article, I explain why I used class objects in ms-access....
>
--
Albert D. Kallal (Access MVP)
Edmonton, Alberta Canada
pleaseNOOSpamKa llal@msn.com
>
>
>

Many thanks Albert (and Gord), I shall read though all of this today.

Regards,
Keith.

[Keith Wilby]

Re: Custom Classes

"Albert D. Kallal" <PleaseNOOOsPAM mkallal@msn.com wrote in message
news:GGoch.4118 63$R63.146206@p d7urf1no...

>
tour1.TourID = 123 ' load tour 123
tour2.TourID = 34 'load tour 34
>
At this point, I have TWO tours loaded in ram, and thus go
>
msgbox "hotel for tour 123 is " & Tour1.HotelName
>
msgbox "hotel for tour 34 is" & Tour2.HotelName
>

<snip>

>
the actual code in the class object for TourID is:
>
Public Property Let TourId(LoadID As Long)
>

Albert,

Dumb question: how do you supply the argument to the property? You have
"tour1.Tour ID = 123" but wouldn't you get an "argument not optional" error
there?

Thanks for your patience, I'll get the hang of this yet!

Keith.

[Gord]

Re: Custom Classes


Keith Wilby wrote:

"Albert D. Kallal" <PleaseNOOOsPAM mkallal@msn.com wrote in message
news:GGoch.4118 63$R63.146206@p d7urf1no...

>

tour1.TourID = 123 ' load tour 123
tour2.TourID = 34 'load tour 34

At this point, I have TWO tours loaded in ram, and thus go

msgbox "hotel for tour 123 is " & Tour1.HotelName

msgbox "hotel for tour 34 is" & Tour2.HotelName

<snip>

the actual code in the class object for TourID is:

Public Property Let TourId(LoadID As Long)

>
Albert,
>
Dumb question: how do you supply the argument to the property? You have
"tour1.Tour ID = 123" but wouldn't you get an "argument not optional" error
there?

Property Let statements behave differently than Function and Sub
statements do. 123 *is* the argument.

[Keith Wilby]

Re: Custom Classes

"Gord" <gdt@kingston.n etwrote in message
news:1165251261 .788681.111140@ l12g2000cwl.goo glegroups.com.. .

>

>>
>Dumb question: how do you supply the argument to the property? You have
>"tour1.TourI D = 123" but wouldn't you get an "argument not optional"
>error
>there?

>
Property Let statements behave differently than Function and Sub
statements do. 123 *is* the argument.
>

Thanks for your patience Gord. Another dumb question but hopefully the
answer will make the penny drop. In a simple example, if I have a table
"tblHoliday s" with fields "ID" and "Country" and I have a class
"clsHoliday ", how do I set and retrieve a "Country" property? I'm calling
the class using:

Dim hlHoliday As clsHoliday
Set hlHoliday = New clsHoliday
hlHoliday.HolID = "ABC123"

Here's the class code:

Property Let HolID(strID As String)

Dim db As DAO.Database, rs As DAO.Recordset
Dim strCountry As String
Set db = CurrentDb
Set rs = db.OpenRecordse t("Select * from tblHolidays Where ID = '" & strID &
"'")
With rs
If .RecordCount 0 Then
'*** What goes here to get the other properties? ***
End If
End With

rs.Close
Set rs = Nothing
db.Close
Set db = Nothing

End Property

[Gord]

Re: Custom Classes

Keith Wilby wrote:

"Gord" <gdt@kingston.n etwrote in message
news:1165251261 .788681.111140@ l12g2000cwl.goo glegroups.com.. .

>
Dumb question: how do you supply the argument to the property? You have
"tour1.Tour ID = 123" but wouldn't you get an "argument not optional"
error
there?

Property Let statements behave differently than Function and Sub
statements do. 123 *is* the argument.

>
Thanks for your patience Gord. Another dumb question but hopefully the
answer will make the penny drop. In a simple example, if I have a table
"tblHoliday s" with fields "ID" and "Country" and I have a class
"clsHoliday ", how do I set and retrieve a "Country" property? I'm calling
the class using:
>
Dim hlHoliday As clsHoliday
Set hlHoliday = New clsHoliday
hlHoliday.HolID = "ABC123"
>
Here's the class code:
>
Property Let HolID(strID As String)
>
Dim db As DAO.Database, rs As DAO.Recordset
Dim strCountry As String
Set db = CurrentDb
Set rs = db.OpenRecordse t("Select * from tblHolidays Where ID = '" & strID &
"'")
With rs
If .RecordCount 0 Then
'*** What goes here to get the other properties? ***
End If
End With
>
rs.Close
Set rs = Nothing
db.Close
Set db = Nothing
>
End Property

Hi, Keith. Try this:

'-----start of class module----
Option Compare Database
Option Explicit

Private mstrHolID As String
Private mstrCountry As String

Public Property Get HolID() As String
' return the property value
HolID = mstrHolID
End Property

Public Property Let HolID(ByVal strID As String)
Dim db As DAO.Database, rs As DAO.Recordset

' save the ID property value
mstrHolID = strID

' retrieve other attributes
Set db = CurrentDb
Set rs = db.OpenRecordse t( _
"Select * from tblHolidays Where ID = '" & strID & "'")
With rs
If .RecordCount 0 Then
'*** What goes here to get the other properties? ***
mstrCountry = rs!Country
End If
End With

rs.Close
Set rs = Nothing
db.Close
Set db = Nothing

End Property

Public Property Get Country() As String
' return the property value
Country = mstrCountry
End Property
'-----end of class module----


'-----start of usage example----
Sub HolidayTest()
Dim hlHoliday As clsHoliday

Set hlHoliday = New clsHoliday
hlHoliday.HolID = "ABC123"
Debug.Print hlHoliday.Count ry

Set hlHoliday = Nothing
End Sub
'-----end of usage example----

[Keith Wilby]

Re: Custom Classes

"Gord" <gdt@kingston.n etwrote in message
news:1165316503 .135209.145400@ n67g2000cwd.goo glegroups.com.. .

>
Hi, Keith. Try this:

<snip>

Duh, I feel so stupid now ;-) The penny has finally dropped, for this
example at least. Many thanks again Gord.

Keith.