Conditional expressions

Dart has two operators that let you concisely evaluate expressionsthat 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 valuebased on a boolean expression,consider using ?:.

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

If the boolean expression tests for null,consider using ??.

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

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

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

4. // Very long version uses if-else statement.
5. String playerName(String name) {
6. if (name != null) {
7. return name;
8. } else {
9. return 'Guest';
10. }
11. }