Getter and Setter in Dart

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Introduction

In this section, you will learn about Getter and Setter in dart with the help of examples.

Getter And Setter

Getter and Setter provide explicit read and write access to an object properties. In dart, get and set are the keywords used to create getter and setter. Getter read the value of property and act as accessor. Setter update the value of property and act as mutator.

Info

Note: You can use same name for getter and setter. But, you can’t use same name for getter, setter and property name.

Use Of Getter and Setter

  • Validate the data before reading or writing.
  • Restrict the read and write access to the properties.
  • Making the properties read-only or write-only.
  • Perform some action before reading or writing the properties.

Example 1: Getter And Setter In Dart

In this example below, there is a class named Student with three private properties _firstName, _lastName and _age. There are two getters fullName and age to get the value of the properties. There are also three setters firstName, lastName and age to update the value of the properties. If age is less than 0, it will throw an error.

class Student {
  // Private Properties
  String? _firstName;
  String? _lastName;
  int? _age;

  // Getter to get full name
  String get fullName => this._firstName! + " " + this._lastName!;

  // Getter to read private property _age
  int get age => this._age!;

  // Setter to update private property _firstName
  set firstName(String firstName) => this._firstName = firstName;

  // Setter to update private property _lastName
  set lastName(String lastName) => this._lastName = lastName;

  // Setter to update private property _age
  set age(int age) {
    if (age < 0) {
      throw new Exception("Age can't be less than 0");
    }
    this._age = age;
  }
}

void main() {
  // Create an object of Student class
  Student st = new Student();
  // setting values to the object using setter
  st.firstName = "John";
  st.lastName = "Doe";
  st.age = 20;
  // Display the values of the object
  print("Full Name: ${st.fullName}");
  print("Age: ${st.age}");
}

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Example 2: Getter And Setter In Dart

In this example below, there is a class named BankAccount with one private property _balance. There is one getter balance to read the value of the property. There are methods deposit and withdraw to update the value of the _balance.

class BankAccount {
  // Private Property
  double _balance = 0.0;

  // Getter to read private property _balance
  double get balance => this._balance;

  // Method to deposit money
  void deposit(double amount) {
    this._balance += amount;
  }

  // Method to withdraw money
  void withdraw(double amount) {
    if (this._balance >= amount) {
      this._balance -= amount;
    } else {
      throw new Exception("Insufficient Balance");
    }
  }
}

void main() {
  // Create an object of BankAccount class
  BankAccount account = new BankAccount();
  // Deposit money
  account.deposit(1000);
  // Display the balance
  print("Balance after deposit: ${account.balance}");
  // Withdraw money
  account.withdraw(500);
  // Display the balance
  print("Balance after withdraw: ${account.balance}");
}

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When To Use Getter And Setter

  • Use getter and setter when you want to restrict the access to the properties.
  • Use getter and setter when you want to perform some action before reading or writing the properties.
  • Use getter and setter when you want to validate the data before reading or writing the properties.
  • Don’t use getter and setter when you want to make the properties read-only or write-only.

Video

Watch our video on getter and setter in Dart.