Multiple ways to the private constructor in Dart | Flutter with examples

This tutorial shows how to create a private constructor in Dart and Flutter.

There is no keyword private in Dart language.

you can check another post on declaring private variables in Dart language.

How do you make a private constructor in dart classes? Generally, a Private constructor allows you not to create an object or instance of a class.

Private constructors are useful to create a Singleton pattern.

Dart Private constructor

A constructor can be added with private using named constructor with underscore (_) syntax

class Employee {
  Employee._() {}
}

if you are creating an object of a class, It throws Error: Couldn’t find constructor ‘Employee’.

void main() {
  var employee= Employee();

}

Again, If you are extending the class which has a private constructor, You can call using the super keyword as given below

class AdminEmployee extends Employee {
  AdminEmployee() : super._();
}

Employee and AdminEmployee should be in the same file, If it is an indifferent file, throws a compilation error.

here is a complete code

class Employee {
  Employee._() {}
}

class AdminEmployee extends Employee {
  AdminEmployee() : super._();
}

void main() {
  var employee = Employee(); //Error: Couldn't find constructor 'Employee'.

}

Similarly, You can also create abstract classes which can create private constructors, But Abstract classes are not intended for using the private constructor.