How to use static keyword in variables and methods in dart

Dart static Keyword

static is a keyword in Dart language and refers to the current class.

static keywords apply to method or class instance variables.

Class is a blueprint for an object.

Instance variables have different copies of data for each object.

Suppose, you want to maintain a single copy of data for all instances, Then the data variable must be declared as static in a class. This is the same case with methods.

usually, instance variables and methods are called with the object name

object.instancevariable
object.method()

Static variables and methods are called with class names directly.

class.instancevariable
class.method()

Syntax:

this.instancevariable
this.method()

Dart static variable

variables are declared with the static keyword in the class for instance variables. static variables are also called class variables.

Syntax:

Here is a syntax for declaring a static variable in a class


static datatype variablename;

Static variables are accessed with the class name

classname.variablename

Here is an example for creating and accessing static variables in Dart with the example

These examples are two instance variables and one static variable.

Static variables are accessed using the class name instance variables are accessed using the object of a class

class Employee {
  static String group = "sales";
  int id = 0;
  String name = '';
  Employee(int id, String name) {
    this.id = id;
    this.name = name;
  }
  printEmployee() {
    print("Name is: ${name}");
    print("Id is : ${id}");
    print("Group: ${group}");
  }
}

void main() {
  Employee e1 = new Employee(1, "john");
  Employee e2 = new Employee(2, "Andrew");

  e1.printEmployee();
  e2.printEmployee();
  print(Employee.group);
  //print(Employee.id);// compilation error
  // print(e1.group); // compilation error

  print(e1.id);
  print(e1.group);
}

Output:

Name is: john
Id is: 1
Group: sales
My name is: Andrew
Id is : 2
Group: sales

Dart static methods

static keywords also apply to methods in a dart class.

These methods also called class methods, use a class

class Employee {
  static String group = "sales";
  int id = 0;
  String name = '';
  Employee(int id, String name) {
    this.id = id;
    this.name = name;
  }
  printEmployee() {
    print("Name is: ${name}");
    print("Id is : ${id}");
  }

  static printEmployeeGroup() {
    print("Group: ${group}");
  }
}

void main() {
  Employee e1 = new Employee(1, "john");
  Employee e2 = new Employee(2, "Andrew");

  e1.printEmployee();
  e2.printEmployee();
  Employee.printEmployeeGroup();
 // e1.printEmployeeGroup(); // compilation error
 // Employee.printEmployee(); // compilation error
}

Important points.

static keyword points to the current class
It applies to variables and methods in a class
static methods and variables are called directly using a class name, not an object instance.
Static variables have the same copy of data for all instances of a class
static methods do not allow to use of instance variables

Dart - Static keyword

Dart static Keyword

Dart static variable

Dart static methods