Hands-On Design Patterns with React Native

Creating union types and intersections

A union type describes a value that can be one of several types. This is a great fit for our Tasks reducer type:

export type TaskReduxActionType =    AddTaskActionType |    TasksFetchActionType |    TasksFetchCompleteActionType |    TasksFetchErrorActionType |    TaskFetchActionType |    TaskFetchCompleteActionType |    TaskFetchErrorActionType;

The union type is created with the | operator. It works just as if it was | was or. One type or another.

We can now use the previous type in the Reducer function:

// src/ Chapter_11/ // Example_3/ src/ features/ tasks/ state/ reducers/ tasksReducer.tsconst tasksReducer = (    state = Immutable.Map<string, any>({        entities: Immutable.List<TaskType>([]),        isLoading: false,        hasError: false ...