CodeBlanks Logo Icon CodeBlanks
Login Register

Ternary

Learn to write a conditional expression in one line with ? :.

Ternary

The ternary is a short way to write a conditional expression on one line: condition ? valueA : valueB. If the condition is true valueA is produced; if false valueB. The result can be assigned to a variable or printed directly.

For example var label = n >= 0 ? "positive" : "negative"; picks a label based on the sign of n. The ternary is the short form of if/else for simple two-way choices; avoid very complex ternaries for readability.

Ternary and if/else

The ternary is an expression; it produces a value and can be assigned to a variable. if/else is a statement; it runs a block but produces no value. They serve different needs.

For simple two-way assignments the ternary is shorter: var s = x > 0 ? "pos" : "neg";. But for complex branching with side effects (print, assignment) if/else is more readable. Practical tip: use the ternary only to pick a value; leave side effects to if/else.

Practice Even/odd label

Declare an int variable n with the value 8. Declare a variable label and assign the ternary n % 2 == 0 ? "even" : "odd" to it. Then print label with print(label);. The output on a single line must be even.

Starter code

main.dart
// Declare n, assign even/odd label with ternary, print it

Sample solution

main.dart
int n = 8;
var label = n % 2 == 0 ? "even" : "odd";
print(label);

Expected output

even

Questions and answers

Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.

1 Complete the ternary

Question 
int n = 7;
var label = n % 2 == 0 ____ "even" : "odd";
print(label);
Answer 
int n = 7;
var label = n % 2 == 0 ? "even" : "odd";
print(label);

Explanation: The ? separates the condition from the true value.

2 Match each part to its job

Term Meaning
cond ? Condition and true arm
: valueB False arm
if/else Two-way statement
ternary Two-way expression

3 What is the output of this code?

main.dart
int n = 7;
print(n % 2 == 0 ? "even" : "odd");
  • true
  • even
  • odd Correct answer
  • 0

Explanation: 7 % 2 == 0 is false, so 'odd' is produced.

All lessons in Beginner

1 Dart basics

  1. What is Dart?
  2. Your first program
  3. dart run
  4. Comments
  5. String interpolation
  6. Summary - Dart basics

2 Variables

  1. var and type
  2. final
  3. const
  4. late
  5. Null safety
  6. Summary - Variables

3 Data types

  1. Integer types
  2. Floating-point types
  3. bool and String
  4. Type inference
  5. dynamic
  6. Summary - Data types

4 Project: Calculator

  1. Project design
  2. Add and subtract
  3. Multiply and divide
  4. Error handling
  5. Putting it together

5 Operators

  1. Arithmetic operators
  2. Assignment operators
  3. Comparison operators
  4. Logical operators
  5. Null-aware operators
  6. Summary - Operators

6 Strings

  1. Creating strings
  2. String interpolation
  3. length and methods
  4. substring
  5. contains and indexOf
  6. Summary - Strings

7 Conditionals

  1. The if statement
  2. else and else if
  3. switch
  4. Pattern matching
  5. Ternary
  6. Summary - Conditionals

8 Loops

  1. The for loop
  2. The while loop
  3. The do-while loop
  4. for-in
  5. break and continue
  6. Summary - Loops

9 Project: Shopping cart

  1. Cart design
  2. Adding items
  3. Calculating totals
  4. Listing the cart
  5. Putting it together

10 Lists

  1. Creating lists
  2. List access
  3. add and remove
  4. length and contains
  5. List methods
  6. Summary - Lists

11 Sets and Maps

  1. Set
  2. Set operations
  3. Map
  4. Map operations
  5. Map iteration
  6. Summary - Sets and Maps

12 Functions

  1. Defining functions
  2. Return values
  3. Arrow functions
  4. Optional parameters
  5. First-class functions
  6. Summary - Functions

13 Null safety in depth

  1. Nullable types
  2. Null-aware operators
  3. The ! operator
  4. late
  5. Null check
  6. Summary - Null safety

14 Class basics

  1. class
  2. Constructor
  3. Instance variables
  4. Methods
  5. this
  6. Summary - Class basics

15 Project: To-do CLI

  1. Task model
  2. Adding tasks
  3. Listing tasks
  4. Completing tasks
  5. Putting it together

16 Advanced string operations

  1. split and join
  2. replace
  3. trim and pad
  4. RegExp
  5. StringBuffer
  6. Summary - Advanced strings

17 Enums

  1. Defining enums
  2. Enum values
  3. Enhanced enums
  4. switch with enum
  5. Enum and patterns
  6. Summary - Enums

18 Exceptions

  1. try/catch
  2. throw
  3. finally
  4. The Exception class
  5. on clause
  6. Summary - Exceptions

19 Async basics

  1. Future
  2. async/await
  3. then
  4. Future.error
  5. Future.wait
  6. Summary - Async basics

20 Beginner final

  1. Project design
  2. Classes
  3. Collections
  4. Error handling
  5. Putting it together