See Also Example
Used at the procedure level to declare dynamic-array variables and allocate or reallocate storage space.
Syntax
ReDim [Preserve] varname(subscripts) [As type][, varname(subscripts) [As type] ] . . .
Remarks
The ReDim statement has these parts:
Part Description
Preserve Preserves the data in an existing array when you resize the last dimension.
varname Name of a variable.
subscripts Dimensions of an array. You can declare multiple dimensions. The syntax of subscripts is described below.
As type Reserved word used to declare the data type of a variable. The type may be Integer, Long, Single, Double, Currency, String (for variable-length strings), String * length (for fixed-length strings), Variant, a user-defined type, or an object type. Use a separate As type clause for each variable being defined.
The argument subscripts has the following syntax:
[lower To ]upper[,[lower To] upper]. . .
The To reserved word provides a way to indicate both the lower and upper bounds of an array variable's subscripts. The following statements are equivalent if there is no Option Base statement:
ReDim A(8,3)
ReDim A(0 To 8, 0 To 3)
ReDim A(8, 0 To 3)
Array subscripts can be negative. To can be used to specify any range of subscripts between -32,768 and 32,767, inclusive. For example:
ReDim A(-4 To 10)
ReDim B(-99 To -5, -3 To 0)
If you use a subscript that is greater than the specified maximum or smaller than the specified minimum, an error occurs.
The ReDim statement is usually used to size or resize a dynamic array that has already been formally declared using a Global or Dim statement with empty parentheses (without dimension subscripts). If you first declare a dynamic array using a Global or Dim statement and include no dimension subscripts, the maximum number of array dimensions you can later specify with ReDim is eight. If your array requires more than eight dimensions, you can use the ReDim statement within a procedure to initially declare a local dynamic-array variable. Your array can then have as many as 60 dimensions.
You can use the ReDim statement repeatedly to change the number of elements in an array. However, you can't use ReDim to change the number of dimensions in an array. For example, if you declare an array consisting of two dimensions (for example, ReDim A(10,10)), you can't use ReDim later to change it to an array with three dimensions. (for example, ReDim A(12,12,12,) ). Similarly, you can't declare an array of Integers and later use ReDim to change the array to another data type.
If you use the Preserve reserved word, you can resize only the last array dimension. For example, if your array has only one dimension, you can resize that dimension because it is the last and only dimension. However, if your array has two or more dimensions, you cannot resize the first one. You can only change the size of the last dimension and still preserve the contents of the array. The following example shows how you can increase the size of the last dimension of a dynamic array without erasing any existing data contained in the array.
ReDim X(10, 10, 10)
...
ReDim Preserve X(10, 10, 15)
When variables are initialized, numeric variables are initialized to 0, Variant variables to Empty. Variable-length strings are initialized as zero-length strings, and fixed-length strings are filled with ANSI zeros (Chr(0)). The fields of user-defined type variables are initialized as if they were separate variables.
Dim Statement
Global Statement
Option Base Statement
Static Statement
The example uses the ReDim statement to dynamically resize an array while a procedure is running. To try this example, paste the code into the Declarations section of a form. Then press F5 and click the form.
Sub Form_Click ()
Dim TestArray() As Integer ' Declare dynamic array.
Dim I, Msg, Size ' Declare variables.
Size = Int(100 * Rnd + 1) ' Generate random number.
ReDim TestArray(Size) ' Make array have Size elements.
For I = 1 To Size ' Index for number of elements.
TestArray(I) = Rnd ' Put number in each element.
Next I
ReDim TestArray(Size * 10) ' Make array 10 times larger.
For I = 1 To Size * 10 ' Index for number of elements.
TestArray(I) = Rnd ' Put number in each element.
Next I
Msg = "This demo created a dynamic array of " & Size
Msg = Msg & " elements and filled each with a random number. "
Msg = Msg & "It then resized the array to " & (Size * 10)
Msg = Msg & " elements, again filling each with a random number. "
Msg = Msg & "Finally, it restored the array back to "
Msg = Msg & Size & " elements."
MsgBox Msg ' Display message.
End Sub