Congratulations! You’ve learned how to build and organize a React+Redux application with multiple slices of state.

By completing this lesson you now know:.

• The action.payload property is used to hold additional data that the reducer might need to carry out a given action. The name payload is simply a convention and its value can be anything!
• The spread syntax (...) and array methods such as .map(), .slice(), and .filter() can be used to immutably update the state of a complex app.
• Reducer composition is a design pattern for managing a Redux store with multiple slices.
• The root reducer delegates actions to slice reducers that are responsible for updating only their assigned slice of the store’s state. The root reducer then reassembles the slices into a new state object.
• combineReducers() is a method provided by the redux library that accepts a collection of reducer functions and returns a rootReducer that implements the reducer composition pattern.
• In a Redux application, slice reducers are often written in separate files. This pattern is known as Redux Ducks.

In the Recipes application you completed in the final exercise, the store is passed from the entry point (index.js) through the main <App /> component as a prop. The <App /> component can then pass the slices of the store’s state to its sub-components.

This approach is called “prop drilling” or “prop threading” because the props are “threaded” through the top-level component in order to get them to the presentational components. This isn’t ideal considering that the top-level component doesn’t make use of those props. In the next lesson, you’ll learn how you can use the react-redux library to avoid “prop threading” and more tricks for building robust React+Redux applications!