The information in this article applies to:
- Standard and Professional Editions of Microsoft Visual Basic for
Windows, versions 2.0 and 3.0
SYMPTOMS
An "Expected: expression" error occurs within a Type statement in Visual
Basic when you follow an array name with empty parentheses ().
You can use the Type ... End Type statement block to define your own data
type using Basic's predefined data types as components. You can dimension
variables or arrays using that user-defined type.
CAUSE
Visual Basic interprets the empty parentheses () that follow a variable
name in the Type statement as a declaration of a dynamic array. Visual
Basic does not allow dynamic arrays to be declared within a user-defined
Type statement block.
RESOLUTION
Within the Type ... End Type statement block, parentheses that follow a
variable name must contain a number to indicate the number of elements
in a static array. Visual Basic allows Type statements to contain static
arrays but not dynamic arrays.
NOTE: Once you correctly define a user-defined type, you can dimension a
dynamic array of that type. See further below for an example.
STATUS
This behavior is by design.
MORE INFORMATION
Steps to Reproduce Behavior
- Start a new project in Visual Basic. Form1 is created by default.
- From the File menu, choose New Module.
- Add the following code to the new module, MODULE1.BAS:
Type newinfo
tarray() as string 'Gives "Expected: Expression" error on ()
numstores As Long
End Type
- Edit the line containing tarray(). Then select any other line. The
automatic syntax checker in Visual Basic correctly highlights the () and
gives the following error:
Expected: Expression
Running the program by pressing the F5 key also correctly reports this
syntax error.
- To correct this programming error, add a number of array elements in the
empty parentheses. For example, change tarray() to tarray(10). This
changes the array from dynamic to static.
Visual Basic interprets the empty parentheses in tarray() in the Type
statement as a declaration of a dynamic array. Visual Basic does not
allow dynamic arrays to be declared within a user-defined Type ... End
Type statement block. The parentheses () must contain a number to
indicate the number of elements in a static array.
How to Make a Dynamic Array of User-Defined Type
- Start a new project in Visual Basic. Form1 is created by default.
- From the File menu, choose New Module.
- Add the following code to the new module, MODULE1.BAS:
Type newinfo
tarray(20) As String 'Static array declared in user-defined type
numstores As Long
End Type
- Double-click Form1 to display the form's code window. Add the following
to the form load event:
Sub Form_Load ()
' Use ReDim to declare or redimension a dynamic array:
ReDim arrayx(20) As newinfo 'Make dynamic array of user-defined type
arrayx(18).tarray(12) = "Ruby slippers" ' Assign value.
arrayx(18).numstores = 999 ' Assign value.
form1.Show ' In load event, must Show form before Print can work.
Print arrayx(18).tarray(12) ' Print value.
Print arrayx(18).numstores ' Print value.
End Sub
NOTE: You cannot change the number of elements in static arrays at run
time, but you can use the ReDim statement to change the number of elements
in dynamic arrays.
REFERENCES
- Visual Basic version 3.0 for Windows, "Programmer's Guide," Chapter 7,
"User-Defined Types (Structures)", pages 176-178. A user-defined type
can contain an ordinary (fixed-size) array, but not a dynamic array.