Dart Programming - Enumeration

Syntax

The syntax for defining an enum in Dart is as follows:

Here's an explanation of each part of the syntax:

• enum: This keyword is used to define an enum in Dart.
• EnumName: Replace this with the desired name of your enum. This name should follow Dart naming conventions for classes, which typically use CamelCase (capitalizing the first letter of each word).
• Value1, Value2, Value3, etc.: These are the individual values or constants that belong to the enum. You can replace them with meaningful names that represent the distinct options you want to define. Each value is separated by a comma.

Declaring Simple Enums

Here's how we can declare a simple enum in Dart:

In this example, we've defined an enum named Color with four possible values: red, green, blue, and yellow.

You can use this enum in your code like this:

Output:

Enums can also have associated values, which can be useful when you want to associate additional data with each enum value. Here's an example:

Output:

Declaring Enhanced Enums in Dart

In Dart, enums are used to represent a fixed set of values. Prior to Dart 2.6, enums were simple constructs with basic features. However, starting from Dart 2.6, you can declare enhanced enums that allow you to add methods, properties, and more to individual enum values. This can make enums more powerful and versatile in your code.

Here's how you can declare and use enhanced enums in Dart:

Output:

In the code above:

• We define an enhanced enum called Color with three values: red, green, and blue.
• We define an extension named ColorExtensions on the Color enum. This extension contains additional methods and properties that can be used with the enum values.
• Inside the extension, we define a displayName getter that returns a user-friendly display name for each enum value.
• We then demonstrate how to use the enhanced enum features by printing the display name of the favorite color and calling the printInfo method.

Enum Iteration and Mapping

Enumerations can be iterated and mapped in Dart, and I'll explain how you can achieve that.

Let's say you have the following enum declaration in Dart:

Enum Iteration:

To iterate over the values of an enum, you can use the .values property of the enum type. Here's an example of how you can iterate through the Color enum:

Output:

Enum Mapping

If you want to map enum values to some other values (e.g., strings, integers, etc.), you can use a Map to create a mapping. Here's an example of how you can map enum values to strings:

Output:

Enum Properties and Methods

Enum Properties

• Values: An enum's values are defined as constants and are usually represented by uppercase identifiers. For instance:

• Indexing: Enums are zero-based indexed collections. In the above example, Color.red has an index of 0, Color.green has an index of 1, and so on.
• Number of Values: You can find the number of values in an enum using the values property:

• String Representation: Enums have a toString() method that returns the name of the enum constant as a string. For example:

Enum Methods

• Index Retrieval: Enums have a method called index that returns the zero-based index of the enum value. For instance:

• Creating Enums from Index: You can retrieve an enum value from its index using the enum's values property:

• Custom Values: Enums can also store custom values using their constructor. These values can have properties and methods of their own:

• Pattern Matching: Enums can be used in switch statements for pattern matching, allowing you to handle different cases elegantly:

• Comparing Enums: You can compare enum values using the equality (==) operator, as enum constants are unique:

• Iterating through Enums: You can iterate through all the values of an enum using a loop:

• Enums with Methods: Enums can have associated methods for specific functionality:

Dart's enum properties and methods provide a structured and organized way to work with a predefined set of related constant values, enhancing code readability and maintainability.

Examples

1. Using enum in a switch statement:
   Output:
   In the first example, we've created an enum Day representing days of the week and used it in a switch statement to print the current day based on the today variable.
2. Define an enumeration for months of the year:
   Output:
   In the second example, we've defined an enum Month representing the months of the year and printed the current month using the currentMonth variable.