React Props Movie Lab

Objectives

Practice passing props from parent components to children
Practice using default props
Practice jumping into and improving existing code

Introduction

This is a bare-bones React application used to showcase the nine greatest movies of all time. Your job is to update it so that it passes props from parent to children components correctly. In addition, you will implement default props so that 'bad/missing data' is properly handled - preventing our user interface from blowing up our visitors' computers

Following is the component tree. When fully rendered, there are 9 MovieCards rendered by MovieShowcase:

└── MovieShowcase
    │
    ├── MovieCard
    │   ├── CardFront
    │   └── CardBack
    │
    └── MovieCard
        ├── CardFront
        └── CardBack

MovieShowcase is the component that will house all of the 'raw' data associated with the movies we want to display. This data is located in src/data.js and is already being imported.

MovieCard components (which showcase a single movie) receive their individual movie information from MovieShowcase as four props: title, IMDBRating, genres, and poster. Following, the props are passed again to either CardFront or CardBack.

In our movie data set, we occasionally have missing data. This is where defaultProps come in and really pull our buns out of the fire. We will be handling all of our defaultProp'ing in MovieCard before they are passed down the chain to the front and back components.

Deliverables

`MovieShowcase`

To get started, take a look at src/data.js to get a sense of the data you'll be working with. We can see that the data is stored in an array of objects. At the end of this file, the data is set up to be exported and in src/MovieShowcase.js, we can see that this data gets imported in at the top:

import movieData from './data.js'

The MovieShowcase component, then, has access to movieData. We want to take this data and, for every object inside, render a MovieCard component, passing the object data in as props. Don't forget to pass all 4 props

Hint: In JSX, it is possible to include JavaScript code and calls to functions. A function called in JSX must be wrapped in curly braces and must return a single JSX element. That single JSX element, however, can contain other elements. So, for instance, the component below renders valid JSX:

import React from 'react';

class App extends React.Component {

  generateInnerJSX = () => {
    return (
      <ul>
        <li>Hello</li>
        <li>Goodbye</li>
      </ul>
    )
  }
  render() {
    return (
      <div>
        {this.generateInnerJSX()}
      </div>
    )
  }
}

export default App;

There is an important exception to this: it is possible to return multiple JSX elements in an array. So instead of having to wrap the li elements above in a ul element, we could write:

import React from 'react';

class App extends React.Component {

  generateInnerJSX = () => {
    return [
      <li>Hello</li>,
      <li>Goodbye</li>
    ]
  }

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

export default App;

More importantly, because we can return arrays, we can use .map to map over data and return an array of elements. The code below will render two li elements just like the previous example, but this time using data from an array:

import React from 'react';

const LIST = ["Hello", "Goodbye"]

class App extends React.Component {

  generateInnerJSX = () => {
    return LIST.map(item => <li>{item}<li>)
  }

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

export default App;

Let's see another example. Suppose you have a component called List instead of an li. We can also map through an array of data and return an array of JSX to dynamically create our List components. We can even pass the strings Hello and Goodbye as props:

class List extends React.Component{
  render(){
    return <li>{this.props.content}</li>
  }
}

const LIST = ["Hello", "Goodbye"]

class App extends React.Component {
  generateInnerJSX = () => {
    return LIST.map(item => <List content={item}/>)
  }

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

The above code is the same as below:

class App extends React.Component {
  render() {
    return (
      <div>
        {[
          <List content={"Hello"} />,
          <List content={"Goodbye"} />
        ]}
      </div>
    )
  }
}

We are dynamically generating an array of JSX to render inside our <div> tag.

You can do the same with movieData: map over the data, passing in values from each object as props. See the documentation here for additional information.

`MovieCard`

If everything is set up properly in MovieShowcase, running the application will produce a page with 9 empty squares popping out. These are the nine MovieCard components being rendered in MovieShowcase and if you click one and hold your mouse button down, you'll see the card animate and 'turn over.'

If we were to place console.log(this.props) in the MovieCard component at the beginning of render(), we'd see that each MovieCard contains different props. Your task here is to pass props to the two child components of MovieCard, CardFront and CardBack.

CardBack will display the title, genres and IMDB rating. CardFront will only be used to display the movie poster. CardFront should receive a poster prop, while CardBack should receive title, genre, and IMDBRating props.

Thinking about the structure of this application, CardFront and CardBack have specific tasks - to display the data they receive as props. MovieShowcase is where this data is imported in. What is the purpose of MovieCard then?

In this case, MovieCard acts as a sort of container. It does render a div element with a CSS class, but besides that, its primary purpose is to house the CardFront and CardBack components.

Note: The poster info you received from movieData is only a hyphenated version of the movie title. All the poster image assets you need are imported into MovieCard already, but you must figure out a way get the right poster based on the props from MovieShowcase and pass it down to CardFront.

Besides containing CardFront and CardBack, the MovieCard component can also be used to make sure that the data being passed down to CardFront and CardBack is complete. For this, we can use default props. Default props allow us to set a default value in the event that a prop is not provided. By doing this in MovieCard, we can ensure that the props passed down to CardFront and CardBack are consistent.

Write defaultProps for the following:

title should default to "Unknown"
IMDBRating should default to null
genres should receive a value that will work with our CardBack component's rendering method for genres. The screen should read: 'No Genre(s) Found'
poster should get the string "default"

Review the previous Props readme for an example on default props, and/or take a look at the documentation for additional guidance.

`CardFront`

This component should have one prop, which should be used to apply a background image. This can be done inline via:

style={{backgroundImage: `url(${prop})`}}

`CardBack`

In this component, you will need to render the title, genres and IMDBRating.

For genres, join each genre together into string with commas separating each.

For IMDBRating, you will need to finish writing the method generateRatingElement(), which should do the following:

if the IMDBRating prop is null, return an <h4> with the contents 'No Rating Found'
otherwise, return <img src={imgMapper[prop]} alt="" /> (using the correct prop)

Just like the posters in MovieCard, we've provided image assets and an object, imgMapper, that includes the right images. The values of imgMapper can be passed directly in as the src attribute on an img element, but you must use the IMDBRating prop as the key to access these values.

Once Finished

Check out the application and make sure everything is functioning how you would like!

Resources

React Default Prop Values

View Props Lab on Learn.co and start learning to code for free.

mendes-develop/Passing-Down-Props