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String interpolation

Learn to embed variables in strings with \$.

String interpolation

With string interpolation you can embed variables or expressions inside a string. This uses the $ sign.

For a simple variable, just write $name. For an expression or property you need curly braces: ${name.length} or ${a + b}.

This is more readable than concatenating with +. Instead of 'Hello ' + name you write 'Hello $name'.

Practice Greet by name

Declare a name variable (set to Alex) and use string interpolation to print Hello Alex. That is, write it as 'Hello $name'.

Starter code

main.dart
// Add the name variable and print

Sample solution

main.dart
void main() {
  var name = 'Alex';
  print('Hello $name');
}

Expected output

Hello Alex

When to use curly braces?

If the text following the $ sign is just an identifier (variable name), no curly braces are needed: $name, $age.

But if you use a property with a dot (name.length), an index (list[0]) or arithmetic (a + b), you must write ${...}.

If unsure, you can always use ${}; ${name} is also valid. What matters is being consistent.

Questions and answers

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

1 Interpolation sign

Question 
var name = 'Derya'; print('Hello ____name');
Answer 
var name = 'Derya'; print('Hello $name');

Explanation: The $ sign embeds the variable into the string.

2 Correct way to embed name.length in a string?

main.dart
print('${name.length}');
  • $name.length
  • $name(length)
  • $[name.length]
  • ${name.length} Correct answer

Explanation: Property access requires ${}.

3 Interpolation concepts

Term Meaning
$name Simple variable
${a + b} Expression embedding
${name.length} Property access
'Merhaba' Literal string

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