What is the difference between Sink and Stream in Flutter?

Question

The Google I/O 2018 video about Flutter explains how to use Dart streams to manage state in a Flutter application. The speaker talked about using Sink as input stream and Stream as output stream. What is the difference between Sink and Stream? I searched the documentation but it doesn't say too much thanks.

Answer 1

Sink and Stream both are parts of the StreamController. You add a data to the StreamController using Sink which can be listened via the Stream.

Example:

final _user = StreamController<User>(); Sink get updateUser => _user.sink; Stream<User> get user => _user.stream; 

Usage:

updateUser.add(yourUserObject); // This will add data to the stream. 

Whenever a data is added to the stream via sink, it will be emitted which can be listened using the listen method.

user.listen((user) => print(user));  

You can perform a various number of actions before the stream is emitted. transform method is an example which can be used to transform the input data before it gets emitted.