Overview
Unlike other programming languages, VBScript lacks support of complex data structures. Sometimes this makes life a bit difficult. We need to code our own algorithms to achieve simple tasks like sorting or reversing an array. .NET has support for complex data structures which come with built-in functions for these simple tasks. So if we can use .NET data structure then we can eliminate the reinvention of the wheel for some of these tasks. Well, the good news is that some .NET libraries are exposed to COM and can be used in VBScript. Let’s take a look at the most useful of these…
ArrayList
An ArrayList is an array whose size is dynamically increased when needed. Here is an example of its use:
Set objArrayList = CreateObject("System.Collections.ArrayList") objArrayList.Add 6 objArrayList.Add 8 objArrayList.Add 2 objArrayList.Add 4 objArrayList.Add 1 objArrayList.Add 5 objArrayList.Add 3 objArrayList.Add 3 objArrayList.Add 7 'Convert to VBScript Array Rhino.Print Join(objArrayList.ToArray, ",") 'Return the element at a given index Rhino.Print objArrayList(0) 'Return the number of elements Rhino.Print objArrayList.Count 'Verifies an element exists or not. Rhino.Print objArrayList.Contains(5) 'Sort the elements objArrayList.Sort Rhino.Print Join(objArrayList.ToArray, ",") 'Reverse the order of all elements objArrayList.Reverse Rhino.Print Join(objArrayList.ToArray, ",") 'Remove a specific element objArrayList.Remove 8 'Remove element by index objArrayList.RemoveAt 6 'Remove all elements objArrayList.Clear
For VBScript Dictionary objects we don’t need to redim while appending or removing elements. Also, an element can be directly searched without iterating through each of them. Both of these features are available with ArrayList as well but one of the most important dictionary object features, Key-Value pair, is not in ArrayList. SortedList is an alternative if you want the power of both ArrayList and Dictionary.
SortedList
A SortedList a is sorted Dictionary. Every time we add or remove a key value pair in the dictionary, it automatically gets sorted by Key. You can also access elements based on its index (just like arrays) which makes this even more powerful. Here is an example:
Set objSortedList = CreateObject("System.Collections.SortedList") objSortedList.Add "Point", 1 objSortedList.Add "Point Cloud", 2 objSortedList.Add "Curve", 4 objSortedList.Add "Surface", 8 objSortedList.Add "Polysurface", 16 objSortedList.Add "Mesh", 32 'Return the number of elements Rhino.Print objSortedList.Count 'Return a value by its key Rhino.Print objSortedList("Surface") 'Access all elements by index For i = 0 To objSortedList.Count - 1 Rhino.Print CStr(objSortedList.GetByIndex(i)) Next 'Verify a key exists Rhino.Print objSortedList.ContainsKey("Polysurface") 'Verify a value exists Rhino.Print objSortedList.ContainsValue(16) 'Return the index by key (zero based index) Rhino.Print objSortedList.IndexOfKey("Polysurface") 'Return the index by value Rhino.Print objSortedList.IndexOfValue(16) 'Remove an element by key objSortedList.Remove "Polysurface" 'Remove an element by index objSortedList.RemoveAt 0 'Remove all elements objSortedList.Clear
Stack
A Stack is a simple last-in, first-out (LIFO) non-generic collection of objects or data. By last-in, first-out, what we mean is if a set of objects is put into a stack, the last object that was put in will be the first object to be taken out. For example, in a restaurants with an automatic plate dispenser, the stack of plates are added to from the top. As each person takes a plate, the next plate in the stack becomes available. Here is an example of using Stack:
Set objStack = CreateObject("System.Collections.Stack") 'Add elements to stack objStack.Push "Item_1" objStack.Push "Item_2" objStack.Push "Item_3" objStack.Push "Item_4" 'Iterate through each element For Each Item In objStack Rhino.Print Item Next 'Convert to VBScript array Rhino.Print Join(objStack.ToArray, ",") 'Return the number of elements Rhino.Print objStack.Count 'Verify an element exists Rhino.Print objStack.Contains("Item_2") 'Pop the last element Rhino.Print objStack.Pop 'Return the last in element without popping Rhino.Print objStack.Peek Rhino.Print objStack.Pop Rhino.Print objStack.Pop 'Remove all elements objStack.Clear
Queue
Unlike a Stack, a Queue represents a first-in, first-out collection of objects or data. Here is an example:
Set objQueue = CreateObject("System.Collections.Queue") 'Add elements to queue objQueue.Enqueue "Item_1" objQueue.Enqueue "Item_2" objQueue.Enqueue "Item_3" objQueue.Enqueue "Item_4" 'Iterate through each element For Each Item In objQueue Rhino.Print Item Next 'Convert to VBScript array Rhino.Print Join(objQueue.ToArray, ",") 'Return the number of elements Rhino.Print objQueue.Count 'Verify an element exists Rhino.Print objQueue.Contains("Item_2") 'Return the first element Rhino.Print objQueue.Dequeue 'Return the first element without removing it Rhino.Print objQueue.Peek Rhino.Print objQueue.Dequeue Rhino.Print objQueue.Dequeue 'Removes all elements objQueue.Clear
