Introduction to React v2

Lifting State Up

Lifting state up is a common refactoring in React app. This section will discuss when you need to do that and how to do that.

Allow user to Edit Movie

Currently our app only allow us to create movie, but it would be better if our app allows us to edit the existing movie too. Let's do that in this section.

Prerequisite: API Service for Edit Movie

Similar to create movie, the prerequisite for our app to support edit movie is the backend service supports it.

Let's test the API with Restlet Client that we've installed in previous section:

  1. select "PUT" in the METHOD dropdown.
  2. enter the following URL in the URL bar:
    https://react-intro-movies.herokuapp.com/movies/{movieId}
    
    • you need to replace {movieId} in the URL with the id of the movie that you want to update.
    • you can get the movie id by inspecting the payload of the GET request. For instance, id for "Aquaman" is 1, while id for "A Star Is Born" is 4.
  3. add the following content in the BODY field (change it to the movie you want to update):
    json
    {
    "id": 4,
    "name": "A Star Is Born v2",
    "releaseDate": "2018-10-03"
    }
  4. click send

Now when you load your app, you should be see your update is shown.

Add Ajax Call Function to Make the PUT Request

Create a saveMovie function in api.js:

src/api.js
js
export const saveMovie = movie =>
axios
.put(`https://react-intro-movies.herokuapp.com/movies/${movie.id}`, movie)
.then(res => res.data);

Since there is some duplications of the URL, let's refactor them:

src/api.js
js
import axios from 'axios';
const MOVIE_ENDPOINT = 'https://react-intro-movies.herokuapp.com/movies';
export const loadMovies = () => axios(MOVIE_ENDPOINT).then(res => res.data);
export const createMovie = movie =>
axios.post(MOVIE_ENDPOINT, movie).then(res => res.data);
export const saveMovie = movie =>
axios.put(`${MOVIE_ENDPOINT}/${movie.id}`, movie).then(res => res.data);
  • similar to axios.put, the second parameter of axios.put is the data you want to submit.

The Interaction of Edit Movie

Let's discuss how we want the edit movie interaction be like.

  1. By default, the form will be used to create movie.
  2. When user click on a movie on the movie list, the form will be populated with the details of the movie, and the form will be used to edit the movie.
  3. User can click "Cancel" button to restore the form to become create movie form again.

Edit Form Interactions

Implementation Overview of Edit Movie

Now that we understand the interaction, let's discuss how are we going to implements it before we write the code.

We need to complete the following tasks:

  1. a state to track if any movie is selected. If a movie selected, make the form as an edit form, else is a create form.
  2. enhance MovieForm so it will display different text based on if movie is selected, e.g. submit button is labelled "Save" instead of "Create", the form title is "Edit Movie" instead of "Create Movie".
  3. add a Reset button in MovieForm to unselect Movie and clear out all its current form value.
  4. a way to update the form values when movie is selected, so that the values will be defaulted to the movie data.
  5. when it is edit, call saveMovie instead of createMovie api function.

Let's implements these.

Add isEdit State

In the App component, let's add a isEdit state (which will be passed to MovieForm component) while setIsEdit will be passed to Movie component as onClick props:

jsx
function App() {
const [moviesShown, toggleShowMovies] = useToggle(false);
const { movies, isLoading, loadMoviesData } = useMovieData();
const [isEdit, setIsEdit] = React.useState(false);
const resetForm = () => {
setIsEdit(false);
};
return (
<div>
<TitleBar>
<h1>React Movie App</h1>
</TitleBar>
<div className="container">
<div>
<div className="button-container">
<Button onClick={toggleShowMovies}>
{moviesShown ? 'Hide' : 'Show'} Movies
</Button>
</div>
{moviesShown && (
<BusyContainer isLoading={isLoading}>
{movies.map(movie => (
<Movie
name={movie.name}
releaseDate={movie.releaseDate}
onClick={() => setIsEdit(true)}
key={movie.id}
/>
))}
</BusyContainer>
)}
</div>
<div>
<MovieForm
onSubmitSuccess={loadMoviesData}
onReset={resetForm}
isEdit={isEdit}
/>
</div>
</div>
</div>
);
}

Let's update Movie component to call the onClick props:

jsx
export const Movie = props => (
<div
className="movie-container selectable"
onClick={props.onClick}
onKeyDown={e => {
if (
e.keyCode === 32 || // space
e.keyCode === 13 // enter
) {
props.onClick();
}
}}
tabIndex={0} >
<h1>{props.name}</h1>
<h2>{props.releaseDate}</h2>
</div>
);
  • the selectable class is added for better visual hint during mouse hover.
  • onClick props on div will be called when the div and its descendents are clicked. tabIndex is added so that so that it will be target of keyboard tab, and onKeyDown is to handle keyboard press enter or space.

And update MovieForm component to show different text and ability to resetForm:

jsx
import { Button } from './components/button';
...
export const MovieForm = ({ isEdit, onSubmitSuccess, onReset }) => {
const { values, setName, setReleaseDate } = useMovieFormData();
const handleSubmit = ev => {
ev.preventDefault();
createMovie(values).then(() => {
onSubmitSuccess();
setName('');
setReleaseDate('');
});
};
return (
<div className="movie-form">
<form onSubmit={handleSubmit}>
<legend>{isEdit ? 'Edit' : 'Create'} Movie</legend>
<div className="field">
<label htmlFor="name" className="label">
Name
</label>
<input
className="input"
value={values.name}
id="name"
name="name"
onChange={ev => setName(ev.target.value)}
required
/>
</div>
<div className="field">
<label htmlFor="releaseDate" className="label">
Release Date
</label>
<input
className="input"
value={values.releaseDate}
id="releaseDate"
name="releaseDate"
type="date"
onChange={ev => setReleaseDate(ev.target.value)}
required
/>
</div>
<div className="button-container">
<button type="submit" className="submit-button">
{isEdit ? 'Save' : 'Create'}
</button>
<Button onClick={onReset}>Cancel</Button>
</div>
</form>
</div>
);
};

If you try your app now, when you click the "Cancel" button, you would realize it would actually cause the page to reload.

This is because by default, clicking button in form would cause the form to be submitted. To avoid this behavior, you need to pass type="button to the button element. And since we would prefer this to be default behavior, let's update our Button component to default the type to "button":

jsx
export const Button = ({ type = 'button', ...props }) => (
<button className="button" type={type} {...props} />
);

Now try your app, you should able to click any movie and the form labels will be updated to edit mode, and click "Cancel" will make it create mode again.

Our current status:

  1. a state to track if any movie is selected. If a movie selected, make the form as an edit form, else is a create form.
  2. enhance MovieForm so it will display different text based on if movie is selected, e.g. submit button is labelled "Save" instead of "Create", the form title is "Edit Movie" instead of "Create Movie".
  3. add a Reset button in MovieForm to unselect Movie and clear out all its current form value.
  4. a way to update the form values when movie is selected, so that the values will be defaulted to the movie data.
  5. when it is edit, call saveMovie instead of createMovie api function.

The next changes (clear form value and set form values with movie data) requires us to update the form value when movie is clicked (which is defined in App component), but currently the movie form data is inside MovieForm component, how do we do that?

Raising State Up

For us to achieve updating form data in App, the solution is raising state up, i.e. move the states related to the form data from MovieForm component to App component:

jsx
// src/app.js
...
// the following code is just cut and paste from movie-form.js
const useMovieForm = () => {
const [name, setName] = React.useState('');
const [releaseDate, setReleaseDate] = React.useState('');
return {
setName,
setReleaseDate,
values: {
name,
releaseDate
}
};
};
function App() {
const [moviesShown, toggleShowMovies] = useToggle(false);
const { movies, isLoading, loadMoviesData } = useMovieData();
const [isEdit, setIsEdit] = React.useState(false);
const { setName, setReleaseDate, values } = useMovieForm();
const selectMovie = movie => {
setIsEdit(true);
setName(movie.name);
setReleaseDate(movie.releaseDate);
};
const resetForm = () => {
setIsEdit(false);
setName('');
setReleaseDate('');
};
return (
<div>
<TitleBar>
<h1>React Movie App</h1>
</TitleBar>
<div className="container">
<div>
<div className="button-container">
<Button onClick={toggleShowMovies}>
{moviesShown ? 'Hide' : 'Show'} Movies
</Button>
</div>
{moviesShown && (
<BusyContainer isLoading={isLoading}>
{movies.map(movie => (
<Movie
name={movie.name}
releaseDate={movie.releaseDate}
onClick={() => selectMovie(movie)}
key={movie.id}
/>
))}
</BusyContainer>
)}
</div>
<div>
<MovieForm
onSubmitSuccess={loadMoviesData}
onReset={resetForm}
isEdit={isEdit}
values={values}
setName={setName}
setReleaseDate={setReleaseDate}
/>
</div>
</div>
</div>
);
}

Update MovieForm to use the props from parent:

jsx
export const MovieForm = ({
isEdit,
onSubmitSuccess,
resetForm,
values,
setName,
setReleaseDate
}) => {
// const { values, setName, setReleaseDate } = useMovieFormData();
const handleSubmit = ev => {
ev.preventDefault();
createMovie(values).then(() => {
onSubmitSuccess();
resetForm();
});
};
...
};

Our current status:

  1. a state to track if any movie is selected. If a movie selected, make the form as an edit form, else is a create form.
  2. enhance MovieForm so it will display different text based on if movie is selected, e.g. submit button is labelled "Save" instead of "Create", the form title is "Edit Movie" instead of "Create Movie".
  3. add a Reset button in MovieForm to unselect Movie and clear out all its current form value.
  4. a way to update the form values when movie is selected, so that the values will be defaulted to the movie data.
  5. when it is edit, call saveMovie instead of createMovie api function.

Calling different API for edit

Let's update our MovieForm component:

jsx
import { createMovie, saveMovie } from './api';
...
export const MovieForm = ({
isEdit,
onSubmitSuccess,
resetForm,
values,
setName,
setReleaseDate
}) => {
const handleSubmit = ev => {
ev.preventDefault();
const req = isEdit ? saveMovie(values) : createMovie(values);
req.then(() => {
onSubmitSuccess();
resetForm();
});
};
...
};

If you try it now, you may realize the save movie doesn't work. This is because saveMovie call actually require id properties in your movie data. Let's update the required code in App component:

jsx
...
const useMovieForm = () => {
const [name, setName] = React.useState('');
const [releaseDate, setReleaseDate] = React.useState('');
const [id, setId] = React.useState(undefined);
return {
setName,
setReleaseDate,
setId,
values: {
id,
name,
releaseDate
}
};
};
function App() {
...
const { setName, setReleaseDate, setId, values } = useMovieForm();
const selectMovie = movie => {
setIsEdit(true);
setName(movie.name);
setReleaseDate(movie.releaseDate);
setId(movie.id);
};
const resetForm = () => {
setIsEdit(false);
setName('');
setReleaseDate('');
setId(undefined);
};
return (
...
);
}

The app should works as expected now!

Do It: Lifting State Up

  1. Declare isEdit state in App component.
  2. Display different text in MovieForm based on isEdit props.
  3. Move useMovieForm hook from MovieForm to App component.
  4. Declare selectMovie and resetForm function in App which will be passed on applicable component.
  5. Create saveMovie function.
  6. In MovieForm component, call saveMovie based on isEdit props.
Comments
Reply
Leonardo Losoviz on June 27, 2019, 3:15 PM

prop name should be onReset instead of resetForm, here:

export const MovieForm = ({ isEdit, onSubmitSuccess, resetForm }) => {

so also here:

<Button onClick={resetForm}>Cancel</Button>
Malcolm Kee on June 28, 2019, 10:18 AM

Thanks for reporting this. It's fixed now! 😀

Issue on this page? Report here