Conditionals: if and else

A conditional runs code only when a condition is true.

Real-world analogy: "If it's raining, take an umbrella; otherwise, wear sunglasses."

Syntax

if (condition) {
  // runs when condition is true
} else if (otherCondition) {
  // runs when the first was false and this one is true
} else {
  // runs when none of the above were true
}

Example

void main() {
  const temperature = 18;

  if (temperature > 25) {
    print("It's hot");
  } else if (temperature > 15) {
    print("It's pleasant");
  } else {
    print("It's cold");
  }
}

Expected output

It's pleasant

Dart checks each condition top to bottom and runs only the first branch that matches. For choosing between two values, the conditional operator ? : from the Operators lesson is often neater.

Common mistakes

• Forgetting the parentheses: if age > 18 doesn't compile.
• Putting conditions in the wrong order. if (score > 50) before if (score > 90) means the second can never run.

Practice

Store an age and print adult for 18 and over, teen for 13–17, and child otherwise.

void main() {
  const age = 15;

  if (age >= 18) {
    print('adult');
  } else if (age >= 13) {
    print('teen');
  } else {
    print('child');
  }
}

teen