Dart if else

Summary: in this tutorial, you’ll learn how to use the Dart if else statement to do something when a condition is true and another thing when the condition is false.

Introduction to the Dart if else statement

In the previous tutorial, you learned how to do something if a condition is true by using the if statement. In practice, you often want to do something if a condition is true and do another thing if the condition is false. The Dart if else statement enables this.

Here’s the syntax of the if else statement:

if (condition)
{
    // statements
}
else
{
    // statements
}Code language: Dart (dart)

In this syntax, the if else statement evaluates the condition first.

If the condition is true, it’ll then execute the block within the curly braces that follow the if clause. If the condition is false, the if else statement executes the statement in the else block.

The following flowchart illustrates how the if else statement works:

Dart if else statement examples

Let’s take some examples of using the if else statement to understand how it works.

1) Simple Dart if else statement examples

The following example uses the if else statement to show a message based on the value of the isWeekend variable:

void main() {
  bool isWeekend = true;
  if (isWeekend) {
    print("Let's play!");
  } else {
    print("Let's go to work!");
  }
}
Code language: Dart (dart)

Output:

Let's play!Code language: Dart (dart)

In this example, the isWekeend is true. Therefore, the program displays the message "Let's play!".

In the following, we change the value of the isWeekend variable to false:

void main() {
  bool isWeekend = false;
  if (isWeekend) {
    print("Let's play!");
  } else {
    print("Let's go to work!");
  }
}Code language: Dart (dart)

Output:

Let's go to work!Code language: Dart (dart)

Since the expression isWeekend is false, the else block executes. Therefore, the program shows the message "Let's go to work!".

2) Using Dart if else statement with a complex condition example

The following example uses the if else statement with a complex condition:

void main() {
  bool isWeekend = true;
  String weather = "sunny";

  if (isWeekend && weather == "sunny") {
    print("Let's go to the beach!");
  } else {
    print("Let's go to work!");
  }
}
Code language: Dart (dart)

Output:

Let's go outside.Code language: Dart (dart)

In this example, we set the isWeekend to true and weather to sunny. Therefore, the following expression evaluates to true:

isWeekend && weather == "sunny"Code language: Dart (dart)

Hence, the if block executes that shows the message "Let's go to the beach!".

In the following example, we change the isWeekend to false:

void main() {
  bool isWeekend = false;
  String weather = "sunny";

  if (isWeekend && weather == "sunny") {
    print("Let's go to the beach!");
  } else {
    print("Let's go to work!");
  }
}Code language: Dart (dart)

Output:

Let's go to work!Code language: Dart (dart)

Because the following expression evaluates to false, the else clause executes that displays the message "Let's go to work!":

isWeekend && weather == "sunny"Code language: JavaScript (javascript)

Summary

• Use Dart if else statement to do something if a condition is true and do another thing if the condition is false.