Summary - Sets and Maps
- Dart course
- Beginner
- Lesson 64/116
- 5 min
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.
Practice Tag Set
Create a Set<String> with three tags. Then print the Set with print.
Starter code
void main() {
// Define a Set with three tags
// print
}Sample solution
void main() {
Set<String> tags = {'yeni', 'onemli', 'acil'};
print(tags);
}Expected output
{yeni, onemli, acil}
Practice 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.
Starter code
void main() {
// Define a Set and a Map
// print Set first, then Map
}Sample solution
void main() {
Set<String> tags = {'onemli', 'acil'};
var phones = <String, String>{'Ayşe': '555-1000', 'Mert': '555-2000'};
print(tags);
print(phones);
}Expected output
{onemli, acil}
{Ayşe: 555-1000, Mert: 555-2000}
Questions and answers
Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.
1 Set and Map
| Term | Meaning |
|---|---|
Set |
Unique elements |
Map |
Key-value pairs |
add |
Element to a Set |
putIfAbsent |
Map insert if absent |
2 Which collection?
- Map for duplicates
- Set for duplicates Correct answer
- Set for indexed access
- Set for key-value
Explanation: a Set prevents duplicates automatically.
3 Map lookup
void main() {
var ages = <String, int>{'Ayşe': 28};
print(ages____);
}void main() {
var ages = <String, int>{'Ayşe': 28};
print(ages['Ayşe']);
}Explanation: square brackets fetch the value for the key.