Reducer

  • The Reducer is a context-independent pure function. It receives the following parameters
    • T state
    • Action action
  • It mainly contains three aspects of information
    • Receive an “intent” and make a state modification.
    • If you want to modify the state, you need to create a new copy and modify it on the copy.
    • If the small state is modified, it will automatically trigger the copy of the main state’s layers data, and then notify the components to refresh in a flattened manner.
  • Sample Code
  1. /// one style of writing
  2. String messageReducer(String msg, Action action) {
  3.   if (action.type == 'shared') {
  4.     return '$msg [shared]';
  5.   }
  6.   return msg;
  7. }
  9. class MessageComponent extends Component<String> {
  10.     MessageComponent(): super(
  11.             view: buildMessageView,
  12.             effect: buildEffect(),
  13.             reducer: messageReducer,
  14.         );
  15. }
  1. /// another style of writing
  2. Reducer<String> buildMessageReducer() {
  3.   return asReducer(<Object, Reducer<String>>{
  4.     'shared': _shared,
  5.   });
  6. }
  8. String _shared(String msg, Action action) {
  9.   return '$msg [shared]';
  10. }
  12. class MessageComponent extends Component<String> {
  13.     MessageComponent(): super(
  14.             view: buildMessageView,
  15.             effect: buildEffect(),
  16.             reducer: buildMessageReducer(),
  17.         );
  18. }

推荐的是第二种写法