storywr/redux-forms-codealong-v-000

Creating Items with Redux

With this lesson we'll begin our journey in implementing the CRUD actions while using the Redux pattern. By the end of this lesson, you will be able to:

• Take user input from our React application and send information to Redux

Our Goal

We'll build a form in Redux that allows us to create a list of todos. So this is a form that would have only one input, for the name of the todo, and the submit button.

Create The Form in React

Ok, if you boot up the application (run npm install && npm start), you'll see that there in the ./src/App.js file we reference a createTodo form located at ./src/components/todos/createTodo.js. That's where we need to build our form.

So in that file we want to change our component to look like the following:

// ./src/components/todos/CreateTodo.js

import React, { Component } from 'react'

class CreateTodo extends Component {
  render() {
    return(
      <div>
        <form>
          <p>
            <label>add todo</label>
            <input type="text" />
          </p>
          <input type="submit" />
        </form>
      </div>
    );
  }
};

export default CreateTodo;

Plan for Integrating into Redux

Now let's think about how we want to integrate this into Redux. Essentially, upon submitting the form, we would like to dispatch the following action to the store:

{
  type: 'ADD_TODO',
  todo: todo
}

So if the user has typed in buy groceries, our action would look like:

{
  type: 'ADD_TODO',
  todo: 'buy groceries'
}

But how do we get that text from the form's input? Here's how. We can use our normal react trick of updating the createTodo component's state whenever someone types something into the form. Then, when the user clicks on the submit button, we can grab that state, and call store.dispatch({ type: 'ADD_TODO', todo: this.state }). Ok, time to implement it. Step one will be updating the component state whenever someone types in the form.

1. Update component state by adding an onChange event handler

Every time the input is changed, we want to change the state. To do this we first add an event handler for every input that changes. So inside the createTodo component, we change our render function to the following.

// ./src/components/todos/createTodo

...

render(){
  return(
    <div>
      <form>
        <p>
          <label>add todo</label>
          <input type="text" onChange={(event) => this.handleChange}/>
        </p>
        <input type="submit" />
      </form>
      {this.state.text}
    </div>
  );
}

...

All this code does is say that every time the user change's the input field (that is, whenever he types something in) we should call our handleChange() function (which we didn't write yet).

Why (event) => this.handleChange) ?

We are using some ES6 magic by using an arrow function to scope the event to our this.handleChange, instead of creating a new lexical scoping, so we can use the current scope of our CreateTodo component Class. This is identical to something like this.handleChange.bind(this)

Ok, our code calls the handleChange() callback each time the user types in the input, but we still need to write that handleChange function. We add a method called handleChange to set the state every time it is called from onChange event.

// ./src/components/todos/createTodo

...

handleChange(event) {
  this.setState({
    text: event.target.value
  });
};

...

Notice that we pass through the event, which comes from the onChange event handler. The event's target is the input that was listening for the event (the text field), and the value is the current value of that text field. So in other words, if the user types in 'hello', the last time the handleChange method is called the event target's value will be 'hello', and the handle change method sets that as the state.

Ok, so now our state will update appropriately each time a user types something into the form. The only other thing to do is to set up the initial state of the component in the constructor.

// ./src/components/todos/createTodo

...

constructor() {
  super();
  this.state = {
    text: '',
  };
}

...

The CreateTodo component should like the following now.

// ./src/components/todos/CreateTodo.js

import React, { Component } from 'react';

class CreateTodo extends Component {

  constructor() {
    super();
    this.state = {
      text: '',
    };
  }

  handleChange(event) {
    this.setState({
      text: event.target.value
    });
  }

  render() {
    return(
      <div>
        <form>
    	  <p>
      	    <label>add todo</label>
            <input
	      type="text"
	      onChange={(event) => this.handleChange(event)} />
          </p>
          <input type="submit" />
       </form>
       {this.state.text}
     </div>
   );
  }
};

export default CreateTodo;

Notice inside the the render function, we wrapped our form in a div, and then at the bottom of that div we added the line {this.state.text}. We do this, just to ensure that we are properly changing the state. If we see our DOM change with every character we type in, we're in good shape.

It's on to step 2.

2. On submission of the form, dispatch an action to the store

Ok, so now we need to make changes to our form so that when the user clicks submit, we dispatch an action to the store. Notice that a lot of the setup for Redux is already done for you. Open up the ./src/index.js file. There you'll see the following:

// ./src/index.js

import React from 'react';
import ReactDOM from 'react-dom';
import App from './App';
import manageTodo from './reducers/manageTodo';
import createStore from './createStore';

let store = createStore(manageTodo);

export function render() {
  ReactDOM.render(
    <App store={store} />,
    document.getElementById('root')
  );
}

store.dispatch({ type: '@@INIT' });

In the top line, you can see that we create the store with a reducer. Then, further down, we pass through the store as a prop to our app. Our App component passes the store as a prop down to the CreateTodo component. So if you put a debugger right after the line render in CreateTodo, and type in this.props in the code, you can see we have access to the store as one of the props.

Why did pass our store in as one of the props? We did it so that on submit we can call this.props.store.dispatch({ type: 'ADD_TODO', todo: this.state }), and send our store with our component's state.

Ok, let's implement this -- it will make more sense as we move along. First, we need to update the render() function of the CreateTodo component to call a callback on the submission of a form:

// ./src/components/todos/CreateTodo.js

...

<form onSubmit={(event) => this.handleSubmit(event)}>

...

Second, we write the handleSubmit() function in the CreateTodo component that dispatches an action upon being called.

// ./src/components/todos/CreateTodo.js

...

handleSubmit(event) {
  event.preventDefault();
  this.props.store.dispatch({
    type: 'ADD_TODO',
    todo: this.state,
  });
}

...

Notice that our action.todo is this.state. This is because our state always holds the value of our input, and we want to pass that value that value into our dispatched action. So for example, if a user types in "add groceries", we will be dispatching, { type: 'ADD_TODO', todo: { text: "add groceries" } }.

Now click the submit button! Yea, nothing happens. At least nothing shows up on the page. Now open up your browser's console. You'll see that we are still logging our actions, and we are dispatching an action called ADD_TODO. If you inspect that action, you should see your input value in the action.todo. So things are happening. However our state is not being updated, and we are not displaying those updates. So first, let's make sure that each time we dispatch an action we update the state.

3. Update the state

So we are properly dispatching the action, but the state is not being updated. What could be the problem? Well remember our crux of redux flow: Action -> Reducer -> New State. So if the action is properly dispatched, then our problem must lie with our reducer. Open up the file ./src/reducers/manageTodo.js.

This function does nothing. Let's fix that. First we need to provide an initial state. Because, we want our state to look like

state = {
  todos: [
    { text: 'buy groceries' },
    { text: 'watch netflix' },
  ]
}

Our initial state should be an empty list of todos, { todos: [] }.

Second, we need to concatenate a new todo each time we receive an action that looks like { type: 'ADD_TODO', todo: { text: 'watch baseball' } }. Ok, let's do it.

// ./src/reducers/manageTodo.js

export default function manageTodo(state = {
  todos: [],
}, action) {
  switch (action.type) {
    case 'ADD_TODO':
      return { todos: state.todos.concat(action.todo.text) };
      
    default:
      return state;
  }
}

Ok, once you change the manageTodo() reducer to the above function, open up the console in your browser, and try clicking the submit button again. Ok, our state is now updating! The only thing left is to display this state on the page as a list of elements on the page. We already did a ton here, so we'll leave that to the next section.

Summary

There's a lot of typing in this section, but three main steps. First, we made sure the react component of our application was working. We did this by building a form, and then making sure that whenever the user typed in the form's input, the state was updated.Once we got React working, we needed to connect it to Redux. We connected Redux by passing through our store object as a prop, and then dispatching an action every time the user submitted the form. Finally, we built our reducer such that it responded to the appropriate event and concatenated the payload into our array of todos. In the next section we'll display our state on the page. That section is a bit of a review, so feel free to finish this application up on your own. After a well-deserved break!