Conditional expressions

Dart has two operators that let you concisely evaluate expressions that might otherwise require if-else statements:

condition ? expr1 : expr2

If condition is true, evaluates expr1 (and returns its value); otherwise, evaluates and returns the value of expr2.

expr1 ?? expr2

If expr1 is non-null, returns its value; otherwise, evaluates and returns the value of expr2.

When you need to assign a value based on a boolean expression, consider using the conditional operator ? and :.

var visibility = isPublic ? 'public' : 'private';

If the boolean expression tests for null, consider using the if-null operator ?? (also known as the null-coalescing operator).

String playerName(String? name) => name ?? 'Guest';

The previous example could have been written at least two other ways, but not as succinctly:

// Slightly longer version uses ?: operator.
String playerName(String? name) => name != null ? name : 'Guest';

// Very long version uses if-else statement.
String playerName(String? name) {
  if (name != null) {
    return name;
  } else {
    return 'Guest';
  }
}