Dart continue

Summary: in this tutorial, you’ll learn how to use the Dart continue statement to start a new iteration of an enclosing loop.

Introduction to the Dart continue statement

The continue statement allows you to skip the current iteration of the loop prematurely and start the next iteration immediately.

The continue statement is only valid when you use it inside a loop, including while, do while, and for loops.

The following shows the syntax of the continue statement:

continue;Code language: Dart (dart)

In practice, you’ll want to start the next iteration if a condition is true. To do it, you use the continue statement with an if statement like this:

if (condition)
{
    continue;
}Code language: Dart (dart)

In this syntax, if the condition is true, the continue statement skips all the statements after the if statement and starts the next iteration.

The following shows how to use the continue statement in a while loop:

while (expression)
{
    if (condition)
    {
        continue;
    }
    // statements that will be skipped by 
    // the continue statement
}Code language: Dart (dart)

In this syntax, if the condition is true, the continue statement will skip all the remaining statements underneath.

The following flowchart illustrates how the continue statement works in a while loop:

Likewise, you can use the continue statement in a do while statement:

do
{
    if (condition)
    {
        continue;
    }

    // statements
} while (expression);Code language: Dart (dart)

The following flowchart illustrates how the continue statement works in a do while loop:

And for loop statement:

for (initializer; loopCondition; iterator)
{
    if(condition)
    {
        continue;
    }
    // statements
}Code language: Dart (dart)

If you use the continue statement inside a nested loop, it’ll only skip the current iteration of the innermost loop.

The following flowchart shows how the continue statement works in a for loop:

Dart continue statement examples

The following example illustrates how the continue statement works.

1) Using the Dart continue statement in a for loop

The following example uses the continue statement in a for loop to display only the odd numbers between 0 and 9:

void main() {
  for (int i = 0; i < 10; i++) {
    if (i % 2 == 0) {
      continue;
    }
    print(i);
  }
}Code language: Dart (dart)

Output:

1
3
5
7
9Code language: Dart (dart)

How it works.

The for loop iterates the numbers from 0 to 9 and assigns the number to the variable i in each iteration.

If the current number (i) is even, the continue statement skips the print statement.

However, if the current number (i) is odd, the condition in the if statement is false. Hence, the continue statement is not reached and the print statement executes that displays the odd number.

2) Using the continue statement in a while loop example

The following example uses the continue statement in a while loop to calculate the total of odd numbers between 0 and 9:

void main() {
  int total = 0, i = 0;
  while (i < 10) {
    i++;
    if (i % 2 == 0) {
      continue;
    }
    total += i;
    print(i);
  }
  print('Total: $total');
}Code language: Dart (dart)

In this example:

• First, each iteration of the while loop will increase the value of the variable i by one until i is 9.
• Second, if the variable i is an even number, the condition of the if statement inside the while loop will execute and skip the remaining statements after it.
• Third, if the variable i is an odd number, it will add an odd number to the total variable.
• Finally, display the total after the loop.

Summary

• Use the continue statement inside a loop to start the next iteration prematurely.