Entry

What is a Dynamic Array and how is it used?

Jun 11th, 2000 13:10
Jerry Yoakum, Exam Cram: MS VB 5, Exam #70-165 - 157610236X

A dynamic array is an array that can be resized "dynamically" so that 
it can grow or shrink as needed. To declare a dynamic array, omit the 
number of elements in the Dim (or Public, Private, or Static) statement:
Dim iDynamic() as Integer
When you determine the number of elements required, you allocate the 
storage with the ReDim keyword. You can repeatedly use ReDim to alter 
the number of elements in an array, and the subscript may be specified 
as a literal, a variable, or the result of a function.
ReDim iDynamic(12) as Integer
ReDim iDynamic(iCount) as Integer
ReDim iDynamic(Sq(36)) as Integer
Redimensioning the array destroys all of the data contained in the 
array unless you use the Preserve keyword. If you increase the number 
of elements in an array and use Preserve, all of the data in the array 
is preserved and the new elements are initialized. If you shrink the 
size of the array, only that data in the remaining elements is 
retained. When you used the Preserve keyword, only the upper bound of 
the last dimension can be modified. You can, however, change the number 
of dimensions if you are not using Preserve.
NOTE:
  Technically, you do not need to specify the data type of an array
  when redimensioning the array; it retains its original data type.
  However, it is good practice to do so.
NOTE:
  Use Erase to clear the contents of an array. If the array is fixed,
  all values are initialized. If the array is dynamic, all memory is
  reclaimed. To use the dynamic array again, you will have to ReDim it.