Dart – Spread Operator (…)

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}