How to create an empty Map in Dart

Question

I'm always forgetting how to create an empty map in Dart. This doesn't work:

final myMap = Map<String, dynamic>{};

This is ok:

final myMap = Map<String, dynamic>();

But I get a warning to use collection literals when possible.

I'm adding my answer below so that it'll be here the next time I forget.

Answer 1

You can create an empty Map by using a map literal:

{}

However, if the type is not already known, it will default to Map<dynamic, dynamic>, which defeats type safety. In order to specify the type for a local variable, you can do this:

final myMap = <String, int>{};

And for non-local variables, you can use the type annotation form:

Map<String, int> myMap = {};

Notes:

• DO use collection literals when possible.
• Omit type annotations for local variables.