Summary - Sets and Maps

Combine Set and Map to write a phone book.

Summary - Sets and Maps

In this group you met two key collections. A Set holds unique elements; you manage it with add, contains and remove. A Map stores key-value pairs; you work with [], putIfAbsent and forEach.

Use a Set to prevent duplicates and a Map to bind a name to a value. Real tasks like phone books, code tables or tag lists combine the two.

In the final task you will merge them: a Set holds unique tags while a Map stores name-age pairs. You will see how the two collections work side by side.

Exercise Tag Set

Create a Set<String> with three tags. Then print the Set with print.

Show example solution

void main() {
  Set<String> tags = {'yeni', 'onemli', 'acil'};
  print(tags);
}

Exercise Phone book with a Set

Define a Set<String> with two tags. Then build a Map<String, String> with two people: name as key, phone as value. Print the Set first, then the Map.

Show example solution

void main() {
  Set<String> tags = {'onemli', 'acil'};
  var phones = <String, String>{'Ayşe': '555-1000', 'Mert': '555-2000'};
  print(tags);
  print(phones);
}

Test yourself

Set and Map

Set

Unique elements
Map

Key-value pairs
add

Element to a Set
putIfAbsent

Map insert if absent
Which collection?
- Map for duplicates
- Set for duplicates
- Set for indexed access
- Set for key-value
Show answer

Set for duplicates — a Set prevents duplicates automatically.

Map lookup

void main() {
  var ages = <String, int>{'Ayşe': 28};
  print(ages____);
}

Show answer

void main() {
  var ages = <String, int>{'Ayşe': 28};
  print(ages['Ayşe']);
}

Next lesson: Defining functions

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