Microsoft Visual Basic 2010 Step by Step eBook

284 Part II Programming Fundamentals

conditions. Dimensioning a dynamic array takes several steps because although the size of

the array isn’t specified until the program is running, you need to make “reservations” for the

array at design time. To create a dynamic array, you follow these basic steps:

1. Specify the name and type of the array in the program at design time, omitting the
   number of elements in the array. For example, to create a dynamic array named
   Temperatures, you type:
   Dim Temperatures() As Single


2. Add code to determine the number of elements that should be in the array at run time.
   You can prompt the user by using an InputBox function or a text box object, or you
   can calculate the storage needs of the program by using properties or other logic. For
   example, the following statements get the array size from the user and assign it to the
   Days variable of type Short:
   Dim Days As Short
   Days = InputBox("How many days?", "Create Array")


3. Use the variable in a ReDim statement to dimension the array, subtracting 1 because
   arrays are zero-based. For example, the following statement sets the size of the
   Temperatures array at run time by using the Days variable:

ReDim Temperatures(Days - 1)

Important With ReDim, you should not try to change the number of dimensions in

an array that you’ve previously declared.

4. Use the UBound function to determine the upper bound in a For... Next loop, and
   process the array elements as necessary, as shown here:

For i = 0 to UBound(Temperatures)

Temperatures(i) = InputBox(Prompt, Title)

Next

In the following exercise, you’ll use these steps to revise the Fixed Array program so that it

can process any number of temperatures by using a dynamic array.

Use a dynamic array to hold temperatures

1. Open the Code Editor to display the program code for the Fixed Array project.


2. Scroll to the top of the form’s code, in which you originally declared the Temperatures
   fixed array.


3. Remove 0 To 6 from the Temperatures array declaration so that the array is now a
   dynamic array.
   The statement looks like the following:

Dim Temperatures() As Single