List<dynamic>
- Flutter course
- Intermediate
- Lesson 54/99
- 4 min
Read JSON arrays as List<dynamic>.
Turning a JSON array into List<dynamic>
A JSON array (with square brackets) is turned into a List<dynamic> by jsonDecode. You access items by index.
const s = '["a", "b", "c"]';
final liste = jsonDecode(s) as List<dynamic>;
print(liste[0]); // a
print(liste.length); // 3Element types are dynamic; for safe use you cast them with as.
Casting the list with cast
To make the list type-safe you use cast<String>() or .map. cast<String>() treats every element as a String and throws otherwise.
final liste = jsonDecode('["x","y"]') as List<dynamic>;
final kelimeler = liste.cast<String>();
print(kelimeler[1]); // yNow kelimeler is a List<String> and you can access items safely.
Practice Print the second element of the list
Decode the string s with jsonDecode, cast it with as List, and print the second element with print.
Starter code
import 'dart:convert';
void main() {
const s = '["elma", "armut", "kiraz"]';
// JSON dizisini çöz ve ikinci elemanı yazdır
}Sample solution
import 'dart:convert';
void main() {
const s = '["elma", "armut", "kiraz"]';
final liste = jsonDecode(s) as List;
print(liste[1]);
}Expected output
armut
Questions and answers
Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.
1 What does jsonDecode('[1,2,3]') return?
- String
- List<dynamic> Correct answer
- A Future
- Map<String, dynamic>
Explanation: jsonDecode turns a JSON array into a List<dynamic>. An object input would return a Map; but a square-bracketed input is a list.
2 Access the first element
import 'dart:convert';
void main() {
const s = '[10, 20, 30]';
final liste = jsonDecode(s) as List;
final ilk = liste[____];
print(ilk);
}import 'dart:convert';
void main() {
const s = '[10, 20, 30]';
final liste = jsonDecode(s) as List;
final ilk = liste[0];
print(ilk);
}Explanation: The first element of a list has index 0; liste[0] gives 10.
3 JSON array parts
| Term | Meaning |
|---|---|
List<dynamic> |
Dart equivalent of a JSON array |
liste[0] |
Access to the first element |
cast<String>() |
Casts the list to a list of Strings |
liste.length |
Gives the number of elements |