How to create an empty Set in Dart

Question

I want to create an empty set for a Flutter project.

I tried this but I get an error:

Set<String> mySet = [];

Error: A value of type 'List' can't be assigned to a variable of type 'Set'.

I found an old question of mine for lists but it doesn't apply to sets.

Solution

You can create an empty Set a number of different ways. For a local variable use a set literal:

var mySet = <String>{};

And for a non-local variable you can use the type annotated form:

Set<String> mySet = {};

Notes

• Empty lists and maps:

  var myList = <String>[];
  var myMap = <String, int>{};
  

• Set literals require Dart 2.2 minimum, which you can change in your pubspec.yaml file if your current setting is below 2.2:

    environment:
      sdk: ">=2.2.0 <3.0.0"
  

• Sets documentation