CodeBlanks Logo Icon CodeBlanks
Login Register

add and remove

Learn list management with .add and .remove.

add and remove

To append an element to a list you use .add(); to remove one you use .remove(). names.add("Alex"); appends "Alex" to the end. names.remove("Alex"); removes the value "Alex" from the list.

Both methods mutate the original list; they do not return a new list. remove takes out the first matching element; if not found the list stays unchanged. add always appends; inserting in the middle uses insert which we will not cover here.

Mutation

.add() and .remove() change the list in place; this behavior is called mutation. For example after var names = ["Alex"]; names.add("Sam"); the names list becomes ["Alex", "Sam"]; no new list is created, the existing one grows.

Some List methods do not mutate; for example map and where return a new Iterable and leave the original list unchanged. Telling the two apart matters: mutation changes the existing one, non-mutation produces a new value.

Practice Add with add and print

Declare a List with var names = ["Alex"];. Append a new element with names.add("Sam");. Print it with print(names);. The output on a single line must be [Alex, Sam].

Starter code

main.dart
// Declare names, append with add and print

Sample solution

main.dart
var names = ["Alex"];
names.add("Sam");
print(names);

Expected output

[Alex, Sam]

Questions and answers

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

1 Match each method to its job

Term Meaning
.add(x) Appends to the end
.remove(x) Removes first match
[i] Reaches i-th element
.length Element count

2 Write the add call

Question 
var names = ["Alex"];
names____;
print(names);
Answer 
var names = ["Alex"];
names.add("Sam");
print(names);

Explanation: .add("Sam") appends an element to the list.

3 What does names.remove("Alex") do?

main.dart
var names = ["Alex", "Sam"];
names.remove("Alex");
  • Adds to the list
  • Removes from the list Correct answer
  • Sorts the list
  • Copies the list

Explanation: remove takes the first matching element out of the list.

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