In this tutorial you will learn about the Dart Classes and its application with practical example.
Dart Classes
Dart is an object-oriented programming language; and supports the concepts of class, object, interfaces, inheritance, mixins, and abstract classes etc. In Dart, a class can be defined as a blueprint or prototype of associated objects. Class is a wrapper that binds/encapsulates the data and methods together; which can be later accessed by objects of that class. We can think of a class as user-defined data type, that describes the behavior and characteristics shared by all of its instances. Once a class has been defined, we can create instance or objects of that class which has access to class properties and methods.
Declaring a Class In Dart
In Dart, a class can be defined using the class keyword followed by the class name; and the class body enclosed by a pair of curly braces ({}).
Syntax:-
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class ClassName { <fields> <getters/setters> <constructors> <functions> } |
Here, ClassName is replaced with the actual class name then in between the curly brackets {} we provide class definition. A class definition includes associated fields, constructors, getters, setters and methods.
Note:- As per the naming convention rules for identifiers; the class name should capitalize the first letter of each word (including the first word), and use no separators.
Example:-
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class Employee { var empName; var empAge; var empSalary; showEmpInfo(){ print("Employee Name Is : ${empName}"); print("Employee Age Is : ${empAge}"); print("Employee Salary Is : ${empSalary}"); } } |
The example declares a class Employee. The class has a three fielda named empName, empAge and empSalary . The showEmpInfo() is a simple function that prints the value of the class fields.
Creating Class Objects In Dart
Once a class has been defined, we can create instance or objects of that class which has access to class fields and function. In Dart, an object of a class can be created using new keyword followed by the class name. Below is general syntax to declare an object of a class.
Syntax:-
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var objectName = new ClassName(<constructor_arguments>); |
Here, objectName and ClassName is replaced with actual object name and the class name respectively. The <constructor_arguments> should be passed values if the class constructor is parameterized.
Example:-
Let’s create an object of the class Employee we have created above –
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var emp = new Employee(); |
Accessing Instance Variable and Functions
In Dart, once we have got an instance of a class created, we can access properties and method of that class using property/method name separated by a dot (.) operator after the instance name as following –
Syntax for Property:-
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objectName.propName |
Syntax for Method:-
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objectName.methodName() |
Example:-
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class Employee { var empName; var empAge; var empSalary; showEmpInfo(){ print("Employee Name Is : ${empName}"); print("Employee Age Is : ${empAge}"); print("Employee Salary Is : ${empSalary}"); } } void main(){ var emp = new Employee(); emp.empName = "John"; emp.empAge = 30; emp.empSalary = 45000; print("W3Adda - Dart Access Class Property and Method"); emp.showEmpInfo(); } |
Output:-
