Deleting Items with Redux

Objectives

How to delete individual elements (making a delete button for items on the display)
Parts:
1. Components\todos:
  - CreateTodo.js
  - Todo.js
  - TodosContainer.js
2. Reducers:
  - manageTodo.js
3. App.js
4. Index.js

Review and Goal

We are never updating the DOM directly.
Redux Pattern: Have our store hold and update our state. Then have React display that state.

GOAL:

DELETE A TODO:

Add a button that when clicked, dispatches an action telling the store to delete a specific todo.
Have a button next to each list element with the todo;
When a user clicks on the button, the list element will be removed.
The Todos component displays the current list of todos, if we remove a todo from the store's state, the display of that todo should be removed as well.

STEP 1:

Create TodosContainer

Sticking with our container vs presentational set up - do not load the presentational Todo component up with logic.
The TodosContainer connects us to Redux. (Redux is the Redux Store) a. Write a new mapDispatchToProps() function to include an action. b. Now, TodosContainer will have access to this.props.delete, which can take in an argument and send it as the action's payload. c. We can then pass this.props.delete down to Todo, so that each Todo component rendered will have access to our 'DELETE_TODO' action.

// ./src/components/todos/TodosContainer.js

import React, { Component } from 'react';
import { connect } from 'react-redux'
import Todo from './Todo'

class TodosContainer extends Component {

  renderTodos = () => this.props.todos.map((todo, id) => <Todo key={id} text={todo} />)

  render() {
    return(
      <div>
        {this.renderTodos()}
      </div>
    );
  }
};

const mapStateToProps = state => {
  return {
    todos: state.todos
  }
}

const mapDispatchToProps = dispatch => {
  return {
    delete: todoText => dispatch({type: 'DELETE_TODO', payload: todoText })
  }
}


export default connect(mapStateToProps, mapDispatchToProps)(TodosContainer);

STEP 2:

Create Todo Component in Todo.js

Todo is receiving this.props.delete.
Incorporate a button.
When we click the button we want to be able to delete this particular todo. At the moment, our todos are just strings, stored in an array. Since that is all we have to work with, we add an onClick attribute to the new button. To keep this component small, we can provide an anonymous function in-line.
This allows you to dispatch an action to the reducer from each Todo.

At this point:

We're providing a definition for an anonymous function.
Inside the definition, we're calling props.delete, and passing in the only other prop available, props.text.
Back in our connected TodosContainer, when this delete button is clicked, the value of props.text is passed into our dispatched action as the payload.
There is a console.log in our reducer that displays actions. Clicking the delete button should log an action with the todo's text content as the payload.

Tell the Store Which Todo to Delete

Our todos are stored as strings in an array.
There are a number of ways to remove a specific string from an array, but one of the more brief options is to use filter.
By adding a second case to our manageTodo reducer, we can write a filter that returns every todo that doesn't match what is contained in action.payload.
In our browser, the delete button should now successful cause todos to disappear.
Give the todos specific IDs to avoid filtering out multiple todos with the same text.

In the Reducers/manageTodo.js, give todo an ID:

A Todo should have an id the moment it gets created.
So, we know that our reducer creates the Todo when a CREATE_TODO action is dispatched.
Using Math.random()*10000000000000000 will generate a long random number each time a todo is created. Now, instead of just storing an array of strings, we'll be storing an array of objects.
This causes a problem 'downstream', though: we need to update our TodosContainer to pass the correct content.
Previously, key was based off the index provided by map.
Now its using our randomly generated ID, and is less prone to errors in the virtual DOM.
We'll need both todo.id and todo.text to be passed into Todo so we pass both down as the object, todo.
Now that we've got todo.id, we can modify the Todo component to use props.todo.id on click.
Now, when props.delete is called, an action is dispatched that contains an id only as its payload.
Updating DELETE_TODO in the Reducer: Now that we're passing an id to props.delete, we need to modify our reducer once more.
Instead of comparing todo with action.payload, now that todo is an object, we want to match todo.id with the payload.
With this final change, todo objects can be added and deleted, each with their own unique id!

Summary

Ok, so in this lesson we covered how to delete a specific Todo. - we gave each Todo a unique id - made sure we passed that id into each Todo component. - Then we made sure to send along that information when dispatching an action via props.delete. - Finally, we had our reducer update the state by filtering out the Todo to be deleted.

m-gamao/redux-delete-codealong-v-000