OOP in Dart: Person, Currency & BankAccount with UML Diagrams

OOP in Dart with Person, Currency & BankAccount 💳

In this blog, we’ll explore Dart OOP using three classes: Person, Currency, and BankAccount. We’ll explain constructors, toString(), static vs instance members, and also use UML diagrams to visualize relationships.

Complete Code

OOP Example in Dart: Person, Currency, and BankAccount


class Person {
  String name;
  int age;

  // Constructor
  Person(this.name, this.age);

  // toString method
  @override
  String toString() {
    return "Person(name: $name, age: $age)";
  }
}

class Currency {
  int totalPaisa;

  // Constructor using rupees and paisa
  Currency({int rupees = 0, int paisa = 0})
      : totalPaisa = rupees * 100 + paisa;

  // Add two currencies
  Currency operator +(Currency other) {
    return Currency(paisa: this.totalPaisa + other.totalPaisa);
  }

  // Show rupees and paisa properly
  @override
  String toString() {
    int rupees = totalPaisa ~/ 100;
    int paisa = totalPaisa % 100;
    return "₹${rupees}.${paisa.toString().padLeft(2, '0')}";
  }
}

class BankAccount {
  static int accountCounter = 1000;
  int accountNumber;
  Person owner;
  Currency balance;

  // Constructor
  BankAccount(this.owner, this.balance)
      : accountNumber = ++accountCounter;

  // Deposit money
  void deposit(Currency amount) {
    balance = balance + amount;
  }

  // toString
  @override
  String toString() {
    return "BankAccount(accountNo: $accountNumber, owner: ${owner.name}, balance: $balance)";
  }
}

void main() {
  Person p1 = Person("Shubham", 22);
  Currency initial = Currency(rupees: 500, paisa: 50);
  BankAccount acc = BankAccount(p1, initial);

  print(acc);

  acc.deposit(Currency(rupees: 200, paisa: 75));
  print("After deposit: $acc");
}

class Person {
  String name;
  int age;

  Person(this.name, this.age);

  @override
  String toString() {
    return "Person(name: $name, age: $age)";
  }
}

2. Currency Class 💰

class Currency {
  double amount;
  String code;
  static int totalCurrencies = 0;

  Currency(this.amount, this.code) {
    totalCurrencies++;
  }

  @override
  String toString() {
    return "$amount $code";
  }
}

3. BankAccount Class 🏦

class BankAccount {
  Person owner;
  Currency balance;
  static int totalAccounts = 0;

  BankAccount(this.owner, this.balance) {
    totalAccounts++;
  }

  void deposit(double amt) { ... }
  void withdraw(double amt) { ... }

  @override
  String toString() {
    return "BankAccount(owner: $owner, balance: $balance)";
  }
}