learn-co-students/redux-forms-codealong-nyc-web-060418

Creating Items with Redux

Objectives

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(event)}/>
        </p>
        <input type="submit" />
      </form>
      {this.state.text}
    </div>
  );
}

...

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

We can shorten this. onChange takes a function, so simply saying onChange={this.handleChange} works. The event is passed in as the argument. This will only work, however, if you are using an arrow function to define handleChange. Without the arrow, you will either need to bind the function, this.handleChange.bind(this), or use the (event) => this.handleChange(event).

Ok, our code calls the handleChange() callback each time the user types in the input, but we still need to write that handleChange function. Let's start with the old way, setting a state value:

// ./src/components/todos/createTodo

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

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.

To make it a completely controlled form, we would also want to set the value attribute of out input element to this.state.props. This way, every key stroke within input will call a setState from within handleChange, the component will re-render and the new value for this.state.text will appear.

The CreateTodo component should look 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)} value={this.state.text}/>
          </p>
          <input type="submit" />
       </form>
     </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 { Provider } from 'react-redux';
import { createStore } from 'redux';

let store = createStore(manageTodo);


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

Just below the import statements, you can see that we create the store using createStore, provided by redux. Then, further down, we pass the store into the Provider. This will allow us access when we connect our components.

Ok, let's connect the CreateTodo. First, we want to import connect from react-redux and modify our export statement:

// ./src/components/todos/CreateTodo.js
import { connect } from 'react-redux';

...

export default connect(null, mapDispatchToProps)(CreateTodo);

In this component, we're not currently concerned with writing a mapStateToProps function (the first argument passed to connect) as this component doesn't need any state. Since we only need to dispatch an action here and not getting information from our store, we can use null instead of mapStateToProps as the first argument.

Next, as we write out our mapDispatchToProps() function, we'll need to decide on how to structure our data and the related action. The basic frame of the function will look like the following:

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

mapDispatchToProps = dispatch => {
  return {
    addTodo: () => dispatch(<some action>)
  }
}

On submission of the form in our component, we want to send the value we've captured in the local state to be added to our Redux store. With the above set up, addTodo becomes a function in props that is able take arguments.

mapDispatchToProps = dispatch => {
  return {
    addTodo: formData => dispatch(<some action>)
  }
}

In terms of action, we could write out a separate actions file and import it in, but for now, we'll just write in an action to get a clearer idea of how this is working:

mapDispatchToProps = dispatch => {
  return {
    addTodo: formData => dispatch({ type: "ADD_TODO", payload: formData })
  }
}

In our component, we could call something like this.props.addTodo(this.state). Since this.state is an object with only one property, text.

Now 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) }>

...

The handleSubmit() function:

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

...

handleSubmit = event => {
  event.preventDefault();
  this.props.addTodo(this.state)
}

...

When handleSubmit() is called, whatever is currently stored in this.state will be sent off to our reducer via our dispatched action. The fully redux'd component ends up looking the like the following:

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

class CreateTodo extends Component {

  state = {
    text: ''
  }

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

  handleSubmit = event => {
    event.preventDefault()
    this.props.addTodo(this.state)
  }

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

mapDispatchToProps = dispatch => {
  return {
    addTodo: formData => dispatch({ type: 'ADD_TODO', payload: formData })
  }
}

export default connect(null, mapDispatchToProps)(CreateTodo);

Now, when the form is submitted, whatever the this.state is will be dispatched to the reducer with the action.

Alternate export statement

Remember that, if not given any arguments, connect will return dispatch as a prop to the component we're wrapping with connect. So an alternative way to write the CreateTodo component could be:

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

class CreateTodo extends Component {

  state = {
    text: ''
  }

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

  handleSubmit = event => {
    event.preventDefault()
    this.props.dispatch({ type: 'ADD_TODO', payload: this.state })
  }

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

export default connect()(CreateTodo);

Now, if you start up the app and click the submit button, you should see your actions via a console.log in our reducer.

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', payload: { 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':

      console.log({ todos: state.todos.concat(action.payload.text) });

      return { todos: state.todos.concat(action.payload.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 a few times. The log will show that our reducer is concatenating new values every time the form is submitted!

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.

• Second, We connected the component to Redux and designed our mapDispatchToProps

• Third, we built our reducer such that it responded to the appropriate event and concatenated the payload into our array of todos.