Cross Ref > Data Structures

Languages Focus

A data structure in which individual values (called elements or items) may be located by reference to one or more integer index variables, the number of such indices being the number of dimensions in the array.

Arrays can start with an index value of 0 or 1, sometimes referred to as 0 based or 1 based.

VB Classic:   x = Array() Arrays in VB Classic use a 0-based indice. Use UBound to get the number of elements. UBound returns -1 if the array has no elements, 0 if it has 1, 1 if it has 2, etc. Syntax Example:   Dim MyArray As Variant Dim i As Integer   MyArray = Array("Mike", "Lisa", "Felicia", "Nathan")   If UBound(MyArray) > -1 Then   For i = 0 To UBound(MyArray)     MsgBox (MyArray(i))   Next End If

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Languages Focus

Associative arrays are also known as a dictionary or a hash table in other languages.

VB Classic:   Collection In addition to Add and Item, collections also offer Count and Remove. Notice that Add uses the format of Value, Key (which is backwards from many other languages). Syntax Example: Dim States As New Collection     States.Add "California", "CA" States.Add "Nevada", "NV"      MsgBox (States.Item("CA"))  VB Classic Associative Array (Collection)

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General Info: Pointers / References

A pointer is a variable type that allows you to refer indirectly to another object. Instead of holding data, a pointer holds the address to data -- the address of another variable or object. You can change the address value a pointer points to thus changing the variable or object the pointer is pointing to.

A reference is a type of pointer that cannot change and it must always point to a valid storage (no nulls).

VB Classic:   Not Supported VB6 does not officially offer developer defined pointers. However, VB5 and VB6 does have unsupported and undocumented VarPtr, StrPtr, and ObjPtr types but you probably should avoid them.  Ref: http://vb.mvps.org/tips/varptr.asp

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