Option
Configures a compiler option.
Option Base
Syntax: Option Base { 0 | 1 }
Used at the module level to declare the default lower bound for array subscripts.
Because the default base is 0, the Option Base statement is never required.
If used, the statement must appear in a module or class before any procedures, functions, or properties. Option Base can appear only once in a module and must precede array declarations that include dimensions.
Note
The To clause in the Dim, Private, Public, ReDim, and Static statements provides a more flexible way to control the range of an array’s subscripts. However, if you don’t explicitly set the lower bound with a To clause, you can use Option Base to change the default lower bound to 1. The base of an array created with the ParamArray keyword is zero; Option Base does not affect ParamArray (or the Array function, when qualified with the name of its type library, for example VBA.Array).
The Option Base statement only affects the lower bound of arrays in the module where the statement is located.
Example of use at module level
This example uses the Option Base statement to override the default base array subscript value of 0. The LBound function returns the smallest available subscript for the indicated dimension of an array. The Option Base statement is used at the module level only.
Module MyModule
Option Base 1 ' Set the default array subscripts to 1.
Sub Example()
Dim Lower
Dim MyArray(20), TwoDArray(3, 4) ' Declare array variables.
Dim ZeroArray(0 To 5) ' Override the default base subscript.
' Use LBound function to test lower bounds of arrays.
Console.WriteLine LBound(MyArray) ' Prints 1.
Console.WriteLine LBound(TwoDArray, 2) ' Returns 1.
Console.WriteLinee LBound(ZeroArray) ' Returns 0.
End Sub
End Module
Example of use at class level
Class Example1
Option Base 1
Sub New()
Dim A1(5)
Console.WriteLine LBound(A1) ' Prints 1
End Sub
End Class
Class Example0
Option Base 0
Sub New()
Dim A0(5)
Console.WriteLine LBound(A0) ' Prints 0
End Sub
End Class
Option Explicit
Syntax: Option Explicit
Used at the module level to force explicit declaration of all variables in that module.
If used, the Option Explicit statement must appear in a module before any procedures.
This option makes it mandatory to require variable declarations. There is no complementary option to make the declarations optional.
When Option Explicit appears in a module, you must explicitly declare all variables by using the Dim, Private, Public, ReDim, and Static Static statements. If you attempt to use an undeclared variable name, an error occurs at compile time.
If you don’t use the Option Explicit statement, and when the Option Explicit On project setting is changed to its non-default value of No, all undeclared variables are of Variant type unless the default type is otherwise specified with a Deftype statement.
Note
The Option Explicit On project setting is Yes by default in new projects. Use Option Explicit to avoid incorrectly typing the name of an existing variable or to avoid confusion in code where the scope of the variable is not clear.
Example of use at module level
Module MyModule
Option Explicit ' Force explicit variable declaration.
Dim MyVar ' Declare variable.
Sub Example()
MyInt = 10 ' Undeclared variable generates error.
MyVar = 10 ' Declared variable does not generate error.
End Sub
End Module
Option Compare
Syntax: Option Compare { Binary | Text | Database }
If used, the Option Compare statement must appear in a module before any procedures.
The Option Compare statement specifies the string comparison method (Binary, Text, or** Database) for a module. If a module doesn’t include an **Option Compare statement, the default text comparison method is Binary.
-
Option Compare Binary results in string comparisons based on a sort order derived from the internal binary representations of the characters. In Microsoft Windows, sort order is determined by the code page. A typical binary sort order is shown in the following example:
A < B < E < Z < a < b < e < z < À < Ê < Ø < à < ê < ø -
Option Compare Text results in string comparisons based on a case-insensitive text sort order determined by your system’s locale. When the same characters are sorted by using Option Compare Text, the following text sort order is produced:
(A=a) < ( À=à) < (B=b) < (E=e) < (Ê=ê) < (Z=z) < (Ø=ø) -
Option Compare Database has no effect in twinBASIC. When used within Microsoft Access, it results in string comparisons based on the sort order determined by the locale ID of the database where the string comparisons occur.
Example
This example uses the Option Compare statement to set the default string comparison method. The Option Compare statement is used at the module level only.
Module ModBin
' Set the string comparison method to Binary.
Option Compare Binary ' That is, "AAA" is less than "aaa".
End Module
Module ModText
' Set the string comparison method to Text.
Option Compare Text ' That is, "AAA" is equal to "aaa".
End Module
Option Private
Syntax: Option Private Module
When used in applications that reference multiple packages, Option Private Module prevents a module’s or class’s contents from being referenced outside its package.
If used, the Option Private statement must appear at module level or class level, before any procedures.
When a module contains Option Private Module, the public parts, for example, variables, objects, and user-defined types declared at the module level, are still available within the project containing the module, but they are not available to other applications or projects.
Note
Option Private is a more verbose way of making modules or classes private to the package. An equivalent effect in a less verbose fashion is obtained with Private statement as follows:
Private Module MyModule
' ...
End Module
Private Class MyClass
' ...
End Class
Example
This example demonstrates the Option Private statement, which is used at module level to indicate that the entire module is private. With Option Private Module, module-level parts not declared Private are available to other modules in the project, but not to other projects or applications.
Module MyModule
Option Private Module ' Indicates that the module is private.
End Module