Dart Operators – Detailed Notes

Operators are special symbols or keywords used to perform operations on values and variables. They are an essential part of Dart programming because they allow developers to perform calculations, compare values, combine conditions, assign values, check types, and work with expressions.

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1. What are Operators?

An operator is a symbol or keyword that tells Dart to perform a particular operation.

For example:

int a = 10;
int b = 5;

int result = a + b;

print(result);

Output:

15

In this example, + is an arithmetic operator used to add two values.

2. Types of Operators in Dart

Dart provides several categories of operators:

• Arithmetic Operators
• Unary Operators
• Assignment Operators
• Relational / Comparison Operators
• Logical Operators
• Type Test Operators
• Conditional Operators
• Null-Aware Operators
• Bitwise and Shift Operators
• Cascade Notation

3. Arithmetic Operators

Arithmetic operators are used to perform mathematical calculations.

Example

void main() {
  int a = 20;
  int b = 6;

  print(a + b);
  print(a - b);
  print(a * b);
  print(a / b);
  print(a ~/ b);
  print(a % b);
}

4. Addition Operator (+)

The + operator is used for addition. It can also be used for String concatenation.

int a = 10;
int b = 20;

int result = a + b;

print(result);

Output:

30

String Example

String firstName = "Rahul";
String lastName = "Sharma";

String fullName = firstName + " " + lastName;

print(fullName);

5. Subtraction Operator (-)

int price = 1000;
int discount = 200;

int finalPrice = price - discount;

print(finalPrice);

Output:

800

6. Multiplication Operator (*)

double price = 500;
int quantity = 3;

double total = price * quantity;

print(total);

Output:

1500.0

7. Division Operator (/)

The / operator performs division and produces a numeric result suitable for fractional values.

int totalMarks = 450;
int subjects = 5;

double average = totalMarks / subjects;

print(average);

8. Integer Division Operator (~/)

The ~/ operator performs integer division.

int result = 10 ~/ 3;

print(result);

Output:

3

The fractional part is discarded.

9. Modulo Operator (%)

The modulo operator returns the remainder after division.

int remainder = 10 % 3;

print(remainder);

Output:

1

Practical Example – Even and Odd Numbers

int number = 20;

if (number % 2 == 0) {
  print("Even number");
} else {
  print("Odd number");
}

10. Unary Operators

Unary operators work with a single operand.

Unary Minus (-)

int number = 10;

print(-number);

Output:

-10

Increment Operator

int count = 5;

count++;

print(count);

Output:

6

Decrement Operator

int count = 5;

count--;

print(count);

Output:

4

11. Prefix and Postfix Operators

Increment and decrement operators can be used before or after an expression.

Postfix

int a = 5;

print(a++);
print(a);

The current value is used first, then the variable is incremented.

Prefix

int a = 5;

print(++a);

The variable is incremented before its value is used in the expression.

12. Assignment Operators

Assignment operators are used to assign or update values stored in variables.

13. Basic Assignment (=)

int age = 25;

age = 30;

print(age);

The = operator assigns the value on the right to the variable on the left.

14. Addition Assignment (+=)

int score = 50;

score += 10;

print(score);

Equivalent to:

score = score + 10;

15. Subtraction Assignment (-=)

int balance = 1000;

balance -= 250;

print(balance);

Output:

750

16. Multiplication Assignment (*=)

int number = 5;

number *= 4;

print(number);

Output:

20

17. Division Assignment (/=)

double price = 1000;

price /= 2;

print(price);

Output:

500.0

18. Comparison Operators

Comparison operators compare two values and produce a Boolean result: true or false.

Example

int age = 20;

print(age == 20);
print(age != 18);
print(age > 18);
print(age < 30);
print(age >= 20);
print(age <= 20);

19. Equal To (==)

The == operator checks whether two values are equal.

int a = 10;
int b = 10;

print(a == b);

Output:

true

20. Not Equal To (!=)

int age = 25;

print(age != 18);

Output:

true

21. Greater Than and Less Than

int marks = 75;

print(marks > 50);
print(marks < 90);

22. Greater Than or Equal To

int marks = 40;

print(marks >= 40);

Output:

true

23. Less Than or Equal To

int age = 18;

print(age <= 18);

Output:

true

24. Logical Operators

Logical operators are used to combine or invert Boolean expressions.

25. Logical AND (&&)

The && operator returns true only when both conditions are true.

int age = 25;
bool hasLicense = true;

bool canDrive = age >= 18 && hasLicense;

print(canDrive);

Output:

true

Example with Login

String username = "admin";
String password = "1234";

if (username == "admin" && password == "1234") {
  print("Login successful");
}

26. Logical OR (||)

The || operator returns true when at least one condition is true.

bool isAdmin = false;
bool isManager = true;

if (isAdmin || isManager) {
  print("Access granted");
}

27. Logical NOT (!)

The ! operator reverses a Boolean value.

bool isLoggedIn = false;

print(!isLoggedIn);

Output:

true

28. Combining Logical Operators

int age = 25;
bool isStudent = true;
bool hasId = true;

if ((age >= 18 && isStudent) || hasId) {
  print("Eligible");
}

Parentheses can make complex expressions easier to read and control the intended grouping.

29. Conditional Operator (Ternary Operator)

The ternary operator is a short way to choose between two expressions based on a condition.

condition ? valueIfTrue : valueIfFalse

Example

int age = 20;

String result = age >= 18 ? "Adult" : "Minor";

print(result);

Output:

Adult

Another Example

double marks = 75;

String result = marks >= 40 ? "Pass" : "Fail";

print(result);

30. Null-Aware Operators

Dart provides operators that make it easier to work with nullable values.

Important null-aware operators include:

• ??
• ??=
• ?.
• ! for asserting that a nullable value is non-null when you know that to be true

31. Null-Coalescing Operator (??)

The ?? operator returns the value on the left when it is not null; otherwise, it returns the value on the right.

String? name;

String displayName = name ?? "Guest";

print(displayName);

Output:

Guest

Example

String? username = "Rahul";

String displayName = username ?? "Guest";

print(displayName);

Output:

Rahul

32. Null-Aware Assignment (??=)

The ??= operator assigns a value only when the variable is currently null.

String? name;

name ??= "Guest";

print(name);

Output:

Guest

If name already contains a value, ??= does not replace it.

String? name = "Rahul";

name ??= "Guest";

print(name);

Output:

Rahul

33. Null-Aware Access Operator (?.)

The ?. operator allows an operation to be performed only when the object is not null.

String? name = "Rahul";

print(name?.length);

If name is null, the expression evaluates to null instead of attempting to access a property on a null object.

34. Null Assertion Operator (!)

The ! operator tells Dart that you know a nullable expression is not null at that point.

String? name = "Rahul";

print(name!.length);

This should only be used when you are certain the value is not null. Otherwise, a runtime error can occur.

35. Type Test Operators

Dart provides operators for checking and working with types.

is Example

var value = 100;

if (value is int) {
  print("Value is an integer");
}

is! Example

var value = "Hello";

if (value is! int) {
  print("Value is not an integer");
}

as Example

Object value = "Hello Dart";

String text = value as String;

print(text);

Type casts should be used when the type relationship is known and valid.

36. Bitwise Operators

Dart also provides bitwise operators for working with the binary representation of integer values.

Example

int a = 5;
int b = 3;

print(a & b);
print(a | b);
print(a ^ b);

Bitwise operations are generally more specialized than everyday arithmetic and logical operations.

37. Shift Operators

Shift operators move the bits of an integer value.

• << – left shift
• >> – right shift
• >>> – unsigned right shift

Example

int value = 4;

print(value << 1);
print(value >> 1);

38. Cascade Notation

Cascade notation allows multiple operations to be performed on the same object.

Dart uses .. and ?.. for cascade operations.

Example

var numbers = []
  ..add(10)
  ..add(20)
  ..add(30);

print(numbers);

Output:

[10, 20, 30]

Cascades can make chained object configuration more concise.

39. Operator Precedence

When an expression contains multiple operators, Dart evaluates them according to operator precedence and associativity.

int result = 10 + 5 * 2;

print(result);

Multiplication is evaluated before addition, so the result is:

20

Using Parentheses

int result = (10 + 5) * 2;

print(result);

Output:

30

Parentheses make the intended order explicit and improve readability.

40. Practical Example – Shopping Cart

void main() {
  double productPrice = 1000;
  int quantity = 3;
  double discount = 200;

  double subtotal = productPrice * quantity;
  double finalPrice = subtotal - discount;

  print("Subtotal: $subtotal");
  print("Final Price: $finalPrice");
}

This example uses multiplication and subtraction operators to calculate a shopping-cart total.

41. Practical Example – Student Result

void main() {
  int marks = 75;

  bool passed = marks >= 40;

  String result = passed ? "Pass" : "Fail";

  print("Marks: $marks");
  print("Result: $result");
}

This example combines a comparison operator with a ternary conditional operator.

42. Practical Example – Login Validation

void main() {
  String username = "admin";
  String password = "12345";

  bool validUsername = username == "admin";
  bool validPassword = password == "12345";

  if (validUsername && validPassword) {
    print("Login successful");
  } else {
    print("Invalid credentials");
  }
}

This example uses the equality operator and logical AND operator.

43. Practical Example – Age Eligibility

void main() {
  int age = 21;

  if (age >= 18) {
    print("Eligible");
  } else {
    print("Not eligible");
  }
}

The >= comparison operator checks whether the age is at least 18.

44. Practical Example – Nullable User Name

void main() {
  String? username;

  String displayName = username ?? "Guest";

  print("Welcome, $displayName");
}

The ?? operator provides a fallback value when the username is null.

45. Operators in Flutter Applications

Dart operators are used extensively when developing Flutter applications. For example, they can be used for calculating totals, validating forms, checking application state, selecting UI text, handling nullable API data, and evaluating conditions.

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Example

double price = 500;
int quantity = 2;

double total = price * quantity;

bool hasItems = quantity > 0;

String message = hasItems
    ? "Items available"
    : "Cart is empty";

print(total);
print(message);

46. Common Operator Mistakes

Mistake 1 – Confusing = and ==

int age = 20;

// Assignment
age = 25;

// Comparison
print(age == 25);

= assigns a value, while == compares values.

Mistake 2 – Using & Instead of &&

bool result = age > 18 && age < 60;

Use && for logical AND conditions.

Mistake 3 – Forgetting Null Safety

String? name;

String displayName = name ?? "Guest";

Mistake 4 – Unnecessary Null Assertion

String? name;

// print(name!.length);

Do not use ! unless you are certain the value is not null.

47. Operator Quick Reference

48. Best Practices for Using Operators

• Use parentheses when they make complex expressions easier to understand.
• Use == for comparison and = for assignment.
• Use logical operators to combine Boolean conditions clearly.
• Use ?? when a nullable value needs a fallback.
• Avoid unnecessary use of the null assertion operator !.
• Use the ternary operator for simple conditional expressions.
• Break complicated expressions into smaller variables when readability suffers.
• Use appropriate arithmetic operators for calculations rather than duplicating logic.
• Understand operator precedence when combining several operators.

49. Practice Exercises

1. Create two integers and perform addition, subtraction, multiplication, and division.
2. Use the modulo operator to determine whether a number is even or odd.
3. Use += to increase a score.
4. Use comparison operators to check whether a student has passed.
5. Use && to validate two conditions.
6. Use || to check whether a user is an admin or manager.
7. Use the ! operator to reverse a Boolean value.
8. Use the ternary operator to display "Pass" or "Fail".
9. Use ?? to provide a default username.
10. Use ??= to assign a default value only when a variable is null.
11. Use is to check the type of a variable.
12. Create a small shopping-cart calculation using multiple operators.

50. Complete Dart Example

void main() {
  double price = 1000;
  int quantity = 3;

  // Arithmetic operators
  double subtotal = price * quantity;
  double discount = 200;
  double finalPrice = subtotal - discount;

  // Comparison operator
  bool isExpensive = finalPrice > 2000;

  // Logical operator
  bool hasItems = quantity > 0;
  bool canCheckout = hasItems && finalPrice > 0;

  // Ternary operator
  String checkoutMessage =
      canCheckout ? "Ready for checkout" : "Cart is empty";

  // Null-aware operator
  String? coupon;
  String couponMessage = coupon ?? "No coupon applied";

  print("Subtotal: $subtotal");
  print("Final Price: $finalPrice");
  print("Expensive: $isExpensive");
  print("Can Checkout: $canCheckout");
  print("Message: $checkoutMessage");
  print("Coupon: $couponMessage");
}

51. Key Takeaways

• Operators perform operations on values and expressions.
• Arithmetic operators are used for mathematical calculations.
• Assignment operators assign or update variable values.
• Comparison operators return Boolean results.
• Logical operators combine Boolean conditions.
• The ternary operator provides a compact conditional expression.
• Null-aware operators make working with nullable values easier.
• Type operators allow type checking and casting.
• Bitwise and shift operators work with integer bit representations.
• Cascade notation allows multiple operations on the same object.
• Operators are fundamental to Dart programming and are used throughout Flutter application development. :contentReference[oaicite:2]{index=2}

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Learning Dart operators provides an important foundation for writing conditions, calculations, validations, data-handling logic, and interactive Flutter applications.