If, Else, Else If, and Switch in Dart

Conditional statements are an important part of Dart programming because they allow a program to make decisions based on different conditions. In JustAcademy's Flutter curriculum, Dart Programming Fundamentals includes control statements such as if, loops, and switch. :contentReference[oaicite:0]{index=0}

These concepts are especially useful when developing Flutter applications because application behavior often depends on user input, authentication status, selected options, product availability, permissions, and other conditions.

1. What Are Conditional Statements?

Conditional statements execute different blocks of code depending on whether a condition is true or false.

For example:

int age = 20;

if (age >= 18) {
  print("You are an adult.");
}

Here, the message is printed only when the condition age >= 18 is true.

2. Types of Conditional Statements in Dart

• if statement
• if-else statement
• else-if ladder
• Nested if
• switch statement
• Ternary operator for simple conditions

3. The if Statement

The if statement executes a block of code only when its condition evaluates to true.

Syntax

if (condition) {
  // code to execute
}

Example

int age = 25;

if (age >= 18) {
  print("You can vote.");
}

Since age is 25, the condition is true and the message is displayed.

Another Example

double marks = 85;

if (marks >= 80) {
  print("Excellent performance!");
}

4. if with Comparison Operators

The if statement can be combined with comparison operators such as ==, !=, >, <, >=, and <=.

int price = 1000;

if (price > 500) {
  print("The product is expensive.");
}

Using ==

String role = "admin";

if (role == "admin") {
  print("Admin dashboard available.");
}

5. if with Logical Operators

Multiple conditions can be combined using logical operators such as &&, ||, and !.

Using AND (&&)

int age = 25;
bool hasId = true;

if (age >= 18 && hasId) {
  print("Access granted.");
}

Using OR (||)

String role = "admin";

if (role == "admin" || role == "manager") {
  print("You can access the dashboard.");
}

Using NOT (!)

bool isBlocked = false;

if (!isBlocked) {
  print("User can continue.");
}

6. The if-else Statement

The if-else statement provides two possible execution paths:

• If the condition is true, the if block executes.
• If the condition is false, the else block executes.

Syntax

if (condition) {
  // code when condition is true
} else {
  // code when condition is false
}

Example

int age = 16;

if (age >= 18) {
  print("You are eligible.");
} else {
  print("You are not eligible.");
}

Login Example

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

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

7. else if Statement

The else if statement is used when there are multiple conditions to check.

Syntax

if (condition1) {
  // code
} else if (condition2) {
  // code
} else if (condition3) {
  // code
} else {
  // default code
}

8. Student Grade Example

int marks = 82;

if (marks >= 90) {
  print("Grade A+");
} else if (marks >= 80) {
  print("Grade A");
} else if (marks >= 70) {
  print("Grade B");
} else if (marks >= 60) {
  print("Grade C");
} else {
  print("Fail");
}

Dart checks the conditions from top to bottom. Once a matching condition is found, its block is executed.

9. Age Category Example

int age = 35;

if (age < 13) {
  print("Child");
} else if (age < 20) {
  print("Teenager");
} else if (age < 60) {
  print("Adult");
} else {
  print("Senior Citizen");
}

10. Discount Example

double amount = 7500;

if (amount >= 10000) {
  print("20% discount");
} else if (amount >= 5000) {
  print("10% discount");
} else if (amount >= 2000) {
  print("5% discount");
} else {
  print("No discount");
}

11. Importance of Condition Order

The order of conditions is important in an else if ladder. Dart evaluates the conditions from top to bottom.

int marks = 95;

if (marks >= 40) {
  print("Pass");
} else if (marks >= 90) {
  print("Excellent");
}

The first condition is already true, so the second condition will never be reached. A better approach is to check the more specific or higher range first.

int marks = 95;

if (marks >= 90) {
  print("Excellent");
} else if (marks >= 40) {
  print("Pass");
} else {
  print("Fail");
}

12. Nested if Statement

An if statement inside another if statement is called a nested if statement.

int age = 25;
bool hasLicense = true;

if (age >= 18) {
  if (hasLicense) {
    print("You can drive.");
  } else {
    print("You need a driving license.");
  }
} else {
  print("You are too young to drive.");
}

13. The switch Statement

The switch statement is useful when you need to compare one value against multiple possible cases.

Basic Syntax

switch (value) {
  case value1:
    // code
    break;

  case value2:
    // code
    break;

  default:
    // default code
}

14. Simple switch Example

String day = "Monday";

switch (day) {
  case "Monday":
    print("Start of the week");
    break;

  case "Friday":
    print("Almost weekend");
    break;

  case "Sunday":
    print("Weekend");
    break;

  default:
    print("Regular day");
}

15. switch with Numbers

int option = 2;

switch (option) {
  case 1:
    print("Home");
    break;

  case 2:
    print("Profile");
    break;

  case 3:
    print("Settings");
    break;

  default:
    print("Invalid option");
}

16. switch for a Menu

String choice = "profile";

switch (choice) {
  case "home":
    print("Opening Home");
    break;

  case "profile":
    print("Opening Profile");
    break;

  case "settings":
    print("Opening Settings");
    break;

  case "logout":
    print("Logging out");
    break;

  default:
    print("Unknown option");
}

17. default in switch

The default case runs when none of the available cases matches the switch value.

int number = 10;

switch (number) {
  case 1:
    print("One");
    break;

  case 2:
    print("Two");
    break;

  default:
    print("Other number");
}

18. Modern switch Expressions

Modern Dart also supports switch expressions, which can be useful when a value needs to be selected based on a pattern or case.

String grade = "A";

String result = switch (grade) {
  "A" => "Excellent",
  "B" => "Good",
  "C" => "Average",
  _ => "Needs improvement"
};

print(result);

The _ pattern can act as a catch-all case in this style of switch expression.

19. if-else vs switch

20. if vs if-else vs else-if vs switch

21. Conditional Statements in Flutter

Conditional logic is frequently used inside Flutter applications to decide what should be displayed or what action should occur. JustAcademy's Flutter curriculum combines Dart fundamentals with widgets, UI development, navigation, forms, API integration, Firebase, and application projects. :contentReference[oaicite:1]{index=1}

Example: Showing Different Messages

bool isLoggedIn = true;

if (isLoggedIn) {
  print("Welcome back!");
} else {
  print("Please log in.");
}

Example: User Role

String role = "admin";

if (role == "admin") {
  print("Show admin dashboard");
} else if (role == "editor") {
  print("Show editor dashboard");
} else if (role == "user") {
  print("Show user dashboard");
} else {
  print("Unknown role");
}

22. E-Commerce Example

double cartTotal = 6500;
bool isMember = true;

if (cartTotal >= 5000 && isMember) {
  print("Apply premium discount");
} else if (cartTotal >= 5000) {
  print("Apply standard discount");
} else {
  print("No discount available");
}

23. Login Validation Example

String email = "[email protected]";
String password = "123456";

if (email.isEmpty || password.isEmpty) {
  print("Please fill all fields");
} else if (password.length < 6) {
  print("Password must contain at least 6 characters");
} else {
  print("Login information is valid");
}

24. Student Result Example

int marks = 76;

if (marks >= 90) {
  print("Grade A+");
} else if (marks >= 80) {
  print("Grade A");
} else if (marks >= 70) {
  print("Grade B");
} else if (marks >= 60) {
  print("Grade C");
} else if (marks >= 40) {
  print("Grade D");
} else {
  print("Fail");
}

25. Day Selection Using switch

int day = 3;

switch (day) {
  case 1:
    print("Monday");
    break;

  case 2:
    print("Tuesday");
    break;

  case 3:
    print("Wednesday");
    break;

  case 4:
    print("Thursday");
    break;

  case 5:
    print("Friday");
    break;

  case 6:
    print("Saturday");
    break;

  case 7:
    print("Sunday");
    break;

  default:
    print("Invalid day");
}

26. User Role Using switch

String role = "admin";

switch (role) {
  case "admin":
    print("Full access");
    break;

  case "manager":
    print("Manager access");
    break;

  case "user":
    print("Limited access");
    break;

  default:
    print("Access denied");
}

27. Common Mistakes

Mistake 1: Using = Instead of ==

Use == when comparing values.

String role = "admin";

if (role == "admin") {
  print("Admin");
}

Mistake 2: Incorrect Condition Order

Put more specific conditions before broader conditions when using an else-if ladder.

Mistake 3: Forgetting Braces

if (age >= 18) {
  print("Adult");
} else {
  print("Minor");
}

Mistake 4: Missing switch Cases

Always consider whether a default case or catch-all handling is appropriate for your switch logic.

28. Best Practices

• Use clear and meaningful conditions.
• Keep conditional logic simple and readable.
• Use else-if when multiple ranges or conditions must be checked.
• Use switch when comparing one value against multiple possible cases.
• Avoid unnecessarily deep nested if statements.
• Order else-if conditions carefully.
• Use braces consistently.
• Choose descriptive variable names.
• Test boundary values such as 0, minimum values, and maximum values.

29. Complete Example

void main() {
  String role = "student";
  int marks = 82;

  if (role == "admin") {
    print("Welcome Admin");
  } else if (role == "teacher") {
    print("Welcome Teacher");
  } else if (role == "student") {
    print("Welcome Student");
  } else {
    print("Unknown role");
  }

  if (marks >= 90) {
    print("Grade A+");
  } else if (marks >= 80) {
    print("Grade A");
  } else if (marks >= 70) {
    print("Grade B");
  } else if (marks >= 40) {
    print("Pass");
  } else {
    print("Fail");
  }

  String menu = "profile";

  switch (menu) {
    case "home":
      print("Home selected");
      break;

    case "profile":
      print("Profile selected");
      break;

    case "settings":
      print("Settings selected");
      break;

    default:
      print("Invalid menu option");
  }
}

30. Quick Revision

31. Practice Exercises

1. Write an if statement to check whether a number is positive.
2. Write an if-else program to check whether a person is eligible to vote.
3. Create an else-if program to calculate student grades.
4. Create an else-if program for product discounts.
5. Write a nested if program for login and account status.
6. Create a switch program for selecting a menu option.
7. Create a switch program to display the day of the week.
8. Create a Flutter example that displays different messages based on login status.

32. Key Takeaways

• if is used for a single condition.
• if-else provides two possible execution paths.
• else-if is useful for multiple conditions.
• Nested if allows conditions inside other conditions.
• switch is useful for matching one value against multiple cases.
• default handles unmatched switch cases.
• Conditional statements are fundamental to Dart programming and Flutter application logic.

33. Learn Flutter with JustAcademy

JustAcademy's Flutter training includes Dart programming fundamentals, including variables, data types, operators, control statements such as if, loops and switch, functions, OOP, collections, and asynchronous programming. :contentReference[oaicite:2]{index=2}

Explore the complete course: JustAcademy Flutter Training

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