Gain insights into Dart's object-oriented features, explore extensions, enums, mixins, and asynchronous programming. Discover hands-on code practice to confidently apply Dart in your projects.

dart.tar.gz

dart2_7

Dart is a fully object-oriented, class-based, simple, and clean language. Google’s popular mobile framework, Flutter uses Dart language to implement high-quality native applications, so it’s recommended that you understand Flutter before beginning this course.

In this course, you will dive deep into Dart 2 language features while using interactive hands-on code playgrounds. This course will help you become confident with Dart extensions, enums, mixins, generics, libraries, asynchronous programming, class variables, callable classes, and generator functions.

By the end of this course, you will have a strong understanding of Dart principles, and you’ll be ready to start using this powerful language in your own projects.

Developing Web Applications with Dart

# Extension Property

Dart provides support for Properties in addition to the methods and operators which we explored in the last few lessons.

In this lesson, we will learn to declare the extension property. We will use the same price list from the previous lessons' examples.


## Example

In this extension, we will add a property to return the total number of printed price labels that are needed for the given price listing. Assume we need to print 3 labels for each price amount in this list `[1, 1.99, 4]`.

**Defining:**

An extension property definition has three parts: type of data to be returned by the property, the `get` keyword, and the name of the property. This is followed by the implementation to calculate the result for the property. It should look  like this:
 
`<return_type> get <property_name> => //implementation`
 
In our example, the number of labels is of type `int`. The property name is `labelCount`. We need 3 labels for each item on the list, therefore, we need three times the total size of the list. We can calculate the number of total labels as `length * 3`. The extension has implicit access to the `length` property of the given list.

```dart
extension<T> on List<T> {
  //Extension Property: 3 printed labels for each price.
  int get labelCount => length * 3;
}
```

**Using:**

The property `labelCount` is called on the price listing `prices` to find the total number of printed labels.
```dart
void main() {
  //List of prices
  List prices = [1, 1.99, 4];

  print("\nNumber of Printed Labels:");
  print(prices.labelCount);
}
```

**Output:**
Since there are 3 items on the list, the total number of printed labels is 9.
```notepad
Number of Printed Labels:
9
```



This lesson explains how to use extension properties. You will also learn that extension methods are static.

Introduction

Dart Extensions

Dart Enums

Dart Mixins

Dart Generics

Dart Libraries

Asynchronous Programming In Dart

Miscellaneous

Next Steps

Extension Properties

Extension Property

Example