In Dart, Spread Operator (…) and Null-aware Spread Operator (…?) are used for inserting multiple elements in a collection like Lists, Maps, etc.
Syntaxes:
- Spread operator
...Data_structure
- Null-aware Spread operator
...?Data_structure
Example 1: Using spread operators with List.
Dart
// main function start void main() {
// initialise a List l1
List? l1 = [ "Geeks" , "For" , "Geeks" ];
// initialize another List l2 using l1
List? l2=[ "Wow" ,...l1, "is" , "amazing" ];
// print List l2
print(l2);
} |
Output :
[Wow, Geeks, For, Geeks, is, amazing]
Example 2: Using Spread operator with Map.
Dart
// main function start void main() {
// initialise a Map m1
Map? m1 = { "name" : "John" , "age" :21};
// initialize another Map m2 using m1
Map? m2={ "roll no" :45, "class" :12,...m1};
// print Map m2
print(m2);
} |
Output :
{roll no: 45, class: 12, name: John, age: 21}
Example 3: Using spread operator with Sets.
Dart
// main function start void main() {
// first set s1
Set< int > s1 = {5, 4, 3};
// second set s2
Set< int > s2 = {3, 2, 1};
// result Set
Set< int > result = {...s1, ...s2};
// print result set
print(result);
} |
Output:
{5,4,3,2,1}
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