Published: Tuesday, March 28, 2000
Dynamic Arrays Made Easy, Part 2
Read Part 1
In Part 1 we discussed why a dynamic array class would be nice and looked
at the code to create such a class. In this part, we'll focus on how to use the DynamicArray
class created in Part 1!
To use the DynamicArray class, simply create an instance of the class like so:
Dim objDynArray
Set objDynArray = New DynamicArray
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To add elements to the class instance, simply use the Data property like so:
objDynArray.Data(4) = "Hello!"
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To loop through the array you can use code like:
Dim i
For i = LBound(objDynArray.DataArray) to UBound(objDynArray.DataArray)
'Or, the above line could be replaced by:
'For i = objDynArray.StartIndex() to objDynArray.StopIndex()
Response.Write i & ".) " & objDynArray.Data(i) & "
"
Next
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Finally, to delete an item, use the Delete method like so:
Dim objDynArray
Set objDynArray = New DynamicArray
objDynArray(0) = "Hello"
objDynArray(2) = "world!"
objDynArray(1) = "there"
'The array now has the values ("Hello", "there", "world!")
'Delete the "there" element (index = 1) so we have Hello, world!
objDynArray.Delete 1
'Now, objDynArray has the values ("Hello", "world!")
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With the DynamicArray class you no longer have to worry about constantly Rediming
an array or making sure that you have legal array bounds. This class allows you to just slap a value in the
array position you want. If the array isn't big enough, it grows. If you want to get rid of an array element,
the array compacts itself for you.
A Note on Performance
Notice that each time the developer attempts to insert an array element whose position is too big, the array
issues a Redim statement. This will lead to a ton of Redim statements if the developer
does something like:
Dim i
For i = 0 to SomeBigNumber
objDynArray.Data(i) = SomeValue
Next
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Rather than just adding one element position when Rediming the array in the Data Let Property,
why not add a number of elements? This way fewer Redim statements are issued, resulting in fewer
memory allocations. Of course if you allocate too many array elements at a time, it will lead to wasted
space.
I hope you found this article interesting and informative, and hopefully you will find the class
applicable to your current projects! Feel free to use the DynamicArray class in any of your
ASP pages!
Happy Programming!
Read Part 1
Download the source code for DynamicArray in text format
