An Enumeration (or enum) is a data type that consists of a group of named values (called elements). By default, the elements are numbered consecutively, starting with zero, but you can assign any Integer value to an element.
Contains(value As Enumeration) As Boolean
Returns True if the value is found within the binary Enumeration.
Enumerations are added to classes (and modules) using Insert > Enumeration. From the Enum Editor, you can add the named values. In your code, you refer to an enum by its name and refer to its elements by using dot notation. For example:
So why should you use an Enum instead of an Integer constant? An Integer constant is a great way to refer to a constant value using a name. But since it is equivalent to an Integer, you cannot restrict its usage. With an enum, you can enforce that only the specific set of values are allowed.
Although Enumerations only accept Integer constants, the Enumeration values cannot be treated as Integers in your code because an Enumeration is a separate type. Likewise, Integer values cannot be assigned to an Enumeration. Should you need to get the Integer value of an Enumeration, you need to cast it to an integer.
You refer to an Enum in your code using dot notation. If the Enum is in a module and has Global scope it is referred to as:
If it is in a module and has Public scope, it uses the module name in the notation:
If it is in a class then you have to use the full notation irrespective of the scope:
Passing as parameters
An Enumeration can be used to restrict the values that can be passed (for example to a method) to only those defined in the Enumeration. This is done by defining the passed parameters as of type Enumeration.
So if you have a method declared as
Sub Test(x As Integer) End Sub
and you do
Test(123) // This code compiles even if the value makes no sense
any range checks have to be in your code for the method and then you have to raise an error or do "something intelligent" to signal the out of bounds value
If however you use an enum (CodeNames in this case):
Foo = 0
Bar = 1
Baz = 2
Sub Test(x As CodeNames) // <<<<<<<<<< passing the enum instead of just an integer End Sub Test(123) // This wont compile !!!!
then the compiler has, at compile time, detected the error in your code.
Supported binary operations
Use with extends
You can use the Extends feature to create extension methods that can convert an Enumeration to its String value. For example, consider this Enumeration that is on a module:
Foo = 0
Bar = 1
Baz = 2
On the same module you can create an extension method like this that will return the Enumeration element name as a String:
Public Function StringValue(Extends e As SomeEnum) As String Select Case e Case SomeEnum.Foo Return "Foo" Case SomeEnum.Bar Return "Bar" Case SomeEnum.Baz Return "Baz" End Select End Function
You can also create a method to do the reverse, which is assign a String to an Enum and have it set the correct element:
Public Sub StringValue(Extends ByRef e As SomeEnum, Assigns value As String) Select Case value Case "Foo" e = SomeEnum.Foo Case "Bar" e = SomeEnum.Bar Case "Baz" e = SomeEnum.Baz Else // Set a default for an invalid input e = SomeEnum.Foo End Select End Sub
With the above two methods, you can now write code like this to get an Enumeration value as a String and to set it using a String:
Var e As SomeEnum e = SomeEnum.Baz Var s As String = e.StringValue // s = "Baz" e.StringValue = "Bar" // e = SomeEnum.Bar e.StringValue = "Biz" // e = SomeEnum.Foo (the default specified in the method)
This technique might be useful for situations when you want to save Enumeration values, such as to a database or JSON. You should not rely on it for your regular coding as it avoids the type checking benefits that an Enumeration brings.
Consider a global Enumeration named SecurityLevels that has four elements: Unauthorized, Minimal, Maximum, and Forced. Their Integer values range from 0 to 3.
To assign a level of Minimal to a variable of type SecurityLevels:
Var level As SecurityLevels level = SecurityLevels.Minimal
The level variable can only be assigned Enum elements. You cannot just assign its Integer value:
level = 1 // Compile error
You can, however, get the Integer value of an element by casting it to an Integer:
Var levelInt As Integer levelInt = Integer(SecurityLevel.Minimal) // levelInt = 1
You can also cast an Integer to an Enum.
Var level As SecurityLevel level = SecurityLevel(1) // No compile or runtime error even if the Integer is not valid
To pass an Enumeration to a method, use its type name:
Sub SetSecurityLevel(level As SecurityLevel) If level = SecurityLevel.Minimal Then // Do something End If End Sub
All project types on all supported operating systems.