contextType property

Accessed once and cached when instance is created. The contextType property on a class can be assigned a ReactContext object created by React.createContext. This lets you consume the nearest current value of that Context using context.

Example:

var MyContext = createContext('test');

class MyClass extends react.Component2 {
  @override
  final contextType = MyContext;

  render() {
    return react.span({}, [
      '${this.context}', // Outputs: 'test'
    ]);
  }
}

See: reactjs.org/docs/context.html#classcontexttype