UDTs and Arrays

[Iain17]

Hey everyone. I would like to know if the following is possible.

I have a User Defined Type. This type has three strings in it. "Name", "Address", "Tel"
I then have an array of this type. The size is how many elements i am retrieving from a file.

What i want to do is pass an array of just the Names to a sub procedure.


Maybe some code will help to explain.

Private Type recordType
  Name As String
  Address As String
  Tel As String
End Type

Dim custArray() As recordType

Private Sub cmdSort_Click()
    Call sortArray(custArray().Name)
End Sub

Private Sub sortArray(sortFiled() As String)
    'sort the array
End Sub

Any help is much appreciated. Thanks in advance

Regards,

Iain.

[Sam Finch]

Fraid not, you're gonna harve to redefine your function to cope with UDTs

[Iain17]

Sorry Sam, i think i mislead you. I meant any help that i wanted to hear was much appreciated.


Just kidding. Thanks for clarifying that. That's what i was afraid of though Sam. It is just it would have been easier that way. Back to the drawing board then.

[ttingen]

Maybe...

Prior to the call to the sort procedure create a string array and fill it with the names in the recType array.

Dim nameArray() as string

For i = 0 to UBound(custArray)
   Redim Preserve nameArray(i) = custArray(i).Name
   i = i + 1
Next i

Call SortArray(nameArray)

Good Luck.

[Iain17]

Yeah i thought of that, but then the thought of transfering anywhere between 5,000, and 50,000 names told me not to.

[ttingen]

Yeah, you're right.

[Sam Finch]

The other point about it is that whan you put the contents of your UDT array into the Sting array and have it sorted by the function, how are you going to use it to sort your UDT, you'll need a function just as complicated as the original function.

so you're in fact nearly tripling the time it would take to sort the array, with 5000 odd records this isn't a good Idea.

[Mark Sreeves]

I'm sorry but I don't see what the problem is.

Dim custArray() is in scope for all procudures in the form so there is no need to pass any part of it as a parameter.

[kedaman]

I don't see the problem either, i think it's that you can't pass an array of UDT's without having a procedure for that UDT. It could be like

Private Sub sortArray(sortFiled() As recordType)

[Iain17]

I think you are all missing the point of what i am trying to do.

I wish to be able to pass any one of the three strings in the user defined type to the sorting function. The function will then sort on the array of strings that i have passed, thus saving me writing 3 seperate sorting algorithims, or using If statements.


Example code.

Private Type recordType
  Name As String
  Address As String
  Tel As String
End Type

Dim custArray() As recordType

Private Sub cmdSort_Click()
    Call sortArray(custArray().Name)
End Sub

Private Sub sortArray(sortFiled() As String)
    'simple bubble sort to demonstarte
    
    Dim i As Integer
    Dim blSwap As Boolean
    Dim tempRec As recordType
    
    Do
      blSwap = False
      For i = LBound(custArray) To UBound(custArray) - 1
        If sortFiled(i) > sortFiled(i + 1) Then
          blSwap = True
          tempRec = custArray(i)
          custArray(i) = custArray(i + 1)
          custArray(i + 1) = tempRec
        End If
      Next i
    Loop Until blSwap = False
      
End Sub

[Mark Sreeves]

If you REALLY are going to have an array with 50000 elements in it I reckon you should use a database.

You can sort it however you want then and the database engine's sorting is a damn sight quicker than using VB!


Just a suggestion...

[kedaman]

Ah, i got ya Iain, youre passing the string array; you have to pass it as a variant:

Private Sub sortArray(sortFiled as Variant)

[Iain17]

Nice idea Ked, but as it stands i get an error in the cmdSortBy_click() event.

[kedaman]

Hmmm, when i look closer, i think youre trying to accomplish the same i tried a few days ago, there's probably just no way out but coding a procedure for each UDT

[holgrave]

What you are doing is not impossible - but the way you are coding it is. You are misunderstanding the basic structures you have created!!

In memory your array of UDT will be stored as:

UDT(0) UDT(1) UDT(2)
Name:Address:Tel:Name:Address:Tel:Name:Address:Tel:

So as such the array of names doesn't exist separately.

Passing UDT().Name is nonesense.

If you want to store and pass each array separately then you should declare this structure:

Private Type recordType
Name() As String
Address() As String
Tel() As String
End Type

Then you can pass recordType.Name() which will work.
However I don't think this structure fits in with your problem.

Your original structure fits the problem - but defeats the objective of sorting. Because of the way the data is arranged you can have the 3 different elements sorted at the same time.

You can only have the recordType array sorted by Name, OR by Address, OR by Tel at any one time. You can't have these 3 states existing at the same time.

You can only have sorting if:
a. You split this structure up.
b. Have a heirarchy of sort keys - such as how Access deals with sorting using mulitple fields. Eg. You could sort by name first, then by address, then by Tel.

If you are happy at only having the UDT sorted by one of its elements at any one time then you would have to seek thought the original UDT destroying it as you go while recreating it in a sorted form by name for example.

Private Type recordType
Name() As String
Address() As String
Tel() As String
End Type

Dim custArray() As recordType


Private Sub cmdSort_Click()
Call sortArray(custArray(), 1)
End Sub



Private Sub sortArray(var() As Variant, intSortKey As Integer)
Dim custSortedArray() As recordType
Dim originalUDT() As recordType

Select Case intSortKey
Case 1
'sort orignalUDT by Name
Case 2
'sort orignalUDT by Address
Case 3
'sort orignalUDT by Tel
End Select
End Sub


If you have any problems in passing the UDT around then the CopyMemory API will solve it - but in which case you will have to make your strings fixed.
I have written apps. using this method extensively, so just shout if you have problems.
I can't be bothered typing the sort code but if you you do this bit I can help with using CopyMemory on the UDT.

holgrave.

[Sam Finch]

holgrave

I don't quite get what you're saying.

By the looks of it you're trying to sort the udt by storing it as 3 seperate arrays and then sorting the name one.

How are you coping with the other 2? won't they be maisaligned?


I reckon it would be far easier to alter the function, you only need to alter it slightly if you have it as 2 seperate functions, just copy and paste it then change the name and a few lines of code of one of the functions.

[holgrave]

Sam you've just made my point for me.

I was trying to say that Iian17 has two options.

1. Change the existing structure to have separate arrays for each element. Or
2. Pass the existing UDT whole sale to the sort function identifying which element he wanted the UDT by.

My code demonstrated 2 as I thought it was more in line with what Iian17 wants.

My way avoids misalignment probs - what Iian17 was trying to do before WOULD.

No alignment probs would currently occur as at the moment it shouldn't be necessary to resort to using CopyMemory or change the fundamental structure of the UDT.

hol.

[Paul282]

Hi,

The problem from the first post is that you can't pass just one part of the udt. but then you're only passing a refference anyway so just pass the whole thing...

Private Type recordType
  Name As String
  Address As String
  Tel As String
End Type


Private Enum Rec
   TheName = 1
   TheAddress = 2
   TheTel = 3
End Enum

Dim custArray() As recordType

Private Sub cmdSort_Click()
    Call sortArray(custArray, TheName)
End Sub

Private Sub sortArray(sortFiled() As recordType, Column as Rec)

   select Case Column
      case TheName
         ' sort by name
      case TheAddress
         'sort by address
   end select
End Sub

You have to do this because "YOU NEED THE WHOLE ARRAY IN ORDER TO SORT IT" unless you're using some sorting algorithm I don't know.

What you should do is create another array as an index and rather than swap the orders of the actual records write the UDT array counter of whatever cloumn you sorted into the index then to loop the list in order (or binary search it)

For x = 1 to 50000
    custArray(index(x)).name
next

[kedaman]

Hehehe, just admit it guys, you can't make a sortfunction to which you pass any UDT.

There's always a way around but as Iain said,

I wish to be able to pass any one of the three strings in the user defined type to the sorting function. The function will then sort on the array of strings that i have passed, thus saving me writing 3 seperate sorting algorithims, or using If statements.

[Paul282]

Well, you could always use a 2D array and enum the fields so it looked sort of like a UDT in code...

"Better Lame than Never!"

Or write your own object model that works sort of like a recordset (but then, your objective is to have less code so... maybe not)

[holgrave]

I think we have wasted are brains on this long enough.

Next question:

Please can you tell me how to write a routine that loops through some data but I don't want to use For, Next, Do or Loop statements? And while your at it please can you change the laws of gravity.

hol.

[Iain17]

Sorry for not posting earlier, i have only just noticed that this old thread got dug up again.

Holgrave, nice ideas mate, but i think you have completely missed the point.

Paul, i know you cant sort a UDT with out the whole UDT, but the passing of one bit of the UDT as an array was just an idea i had. I now accept that it wont work.

I now unfortunately have many sorting functions.

[kedaman]

HEhe, i knew Iain would reply that sooner or later

But i think you could do some sort of sorting with copymemory, if you just specify which parts to be sorted

[holgrave]

;-)

[hurgh]

Y dont you just put the udt into a listview (set to report mode) then use a function tha sorts the list view by the column header that you clicked.
Then once you have sorted the listview just stick all the stuff back into the UDT and your done

-|- Hurgh -|-