GraphAcademy

Building Neo4j Applications with Node.js

Project Introduction

The Neo4j JavaScript Driver

Interacting with Neo4j

Homework: Project Backlog

Movie Lists and Pagination

Optional Lesson

This lesson is optional and will not count towards your achievement. To view the completed code, check out the 11-movie-lists branch.

In this challenge, you will implement the remaining methods in the MovieService for retrieving a list of movies:

  • getByGenre - should return a paginated list of movies that are listed in a particular Genre

  • getForActor - should return a paginated list of movies that a particular Person has acted in

  • getForDirector - should return a paginated list of movies that a particular Person has directed

These methods are very similar to the all() method which returns a full list, but with a different pattern in the MATCH clause.

For each subtask, we will provide you with the pattern required to run in the Cypher statement, plus any additional parameters that are required for the query to run.

All you need to do is take the code from the all() method and modify the pattern in the first line of the Cypher statement in the first argument of the tx.run() call, then if necessary add the additional parameters to the second argument.

If you get stuck at any point, you can click to reveal the completed solution or skip to the bottom for instructions on how to checkout the branch with the working solution.

Open src/services/movie.service.js →

getByGenre

The getByGenre() method returns a paginated list of movies that are listed within a certain genre.

js
src/services/movie.service.js
async getByGenre(name, sort = 'title', order = 'ASC', limit = 6, skip = 0, userId = undefined) {
  // TODO: Get Movies in a Genre
  // MATCH (m:Movie)-[:IN_GENRE]->(:Genre {name: $name})

  return popular.slice(skip, skip + limit)
}

Update the getByGenre() method to use the following Cypher Pattern:

cypher
MATCH (m:Movie)-[:IN_GENRE]->(:Genre {name: $name})

The tx.run() call will need to include the name property, which represents the name of the genre.

Click to reveal the completed getByGenre() method

Find the getByGenre() method in src/services/movie.service.js and modify the function to find a list of movies by genre.

js
src/services/movie.service.js
async getByGenre(name, sort = 'title', order = 'ASC', limit = 6, skip = 0, userId = undefined) {
  // Get Movies in a Genre
  // MATCH (m:Movie)-[:IN_GENRE]->(:Genre {name: $name})

  // Open a new session
  const session = this.driver.session()

  // Execute a query in a new Read Transaction
  const res = await session.executeRead(async tx => {
    // Get an array of IDs for the User's favorite movies
    const favorites = await this.getUserFavorites(tx, userId)

    // Retrieve a list of movies with the
    // favorite flag appened to the movie's properties
    return tx.run(`
      MATCH (m:Movie)-[:IN_GENRE]->(:Genre {name: $name})
      WHERE m.\`${sort}\` IS NOT NULL
      RETURN m {
        .*,
        favorite: m.tmdbId IN $favorites
      } AS movie
      ORDER BY m.\`${sort}\` ${order}
      SKIP $skip
      LIMIT $limit
    `, { skip: int(skip), limit: int(limit), favorites, name })
  })

  // Get a list of Movies from the Result
  const movies = res.records.map(row => toNativeTypes(row.get('movie')))

  // Close the session
  await session.close()

  return movies
}

getForActor

The getForActor() method returns a paginated list of movies that a person has acted in.

js
src/services/movie.service.js
async getForActor(id, sort = 'title', order = 'ASC', limit = 6, skip = 0, userId = undefined) {
  // TODO: Get Movies acted in by a Person
  // MATCH (:Person {tmdbId: $id})-[:ACTED_IN]->(m:Movie)

  return roles.slice(skip, skip + limit)
}

Find the getForActor() method in src/services/movie.service.js and modify the function to find a list of movies by actor.

The pattern required in the MATCH clause will be:

cypher
MATCH (:Person {tmdbId: $id})-[:ACTED_IN]->(m:Movie)

You will have to include the additional parameter id - The tmdbId property relating to the actor.

Click to reveal the completed getForActor() method
js
src/services/movie.service.js
async getForActor(id, sort = 'title', order = 'ASC', limit = 6, skip = 0, userId = undefined) {
  // Get Movies acted in by a Person
  // MATCH (:Person {tmdbId: $id})-[:ACTED_IN]->(m:Movie)

  // Open a new session
  const session = this.driver.session()

  // Execute a query in a new Read Transaction
  const res = await session.executeRead(async tx => {
    // Get an array of IDs for the User's favorite movies
    const favorites = await this.getUserFavorites(tx, userId)

    // Retrieve a list of movies with the
    // favorite flag appened to the movie's properties
    return tx.run(`
      MATCH (:Person {tmdbId: $id})-[:ACTED_IN]->(m:Movie)
      WHERE m.\`${sort}\` IS NOT NULL
      RETURN m {
        .*,
        favorite: m.tmdbId IN $favorites
      } AS movie
      ORDER BY m.\`${sort}\` ${order}
      SKIP $skip
      LIMIT $limit
    `, { skip: int(skip), limit: int(limit), favorites, id })
  })

  // Get a list of Movies from the Result
  const movies = res.records.map(row => toNativeTypes(row.get('movie')))

  // Close the session
  await session.close()

  return movies
}

getForDirector

The getForDirector() method returns a paginated list of movies that a person has directed.

js
src/services/movie.service.js
async getForDirector(id, sort = 'title', order = 'ASC', limit = 6, skip = 0, userId = undefined) {
  // TODO: Get Movies directed by a Person
  // MATCH (:Person {tmdbId: $id})-[:DIRECTED]->(m:Movie)

  return popular.slice(skip, skip + limit)
}

Find the getForDirector() method in src/services/movie.service.js and modify the function to find a list of movies by director.

The pattern required in the MATCH clause will be:

cypher
MATCH (:Person {tmdbId: $id})-[:DIRECTED]->(m:Movie)

You will have to include the additional parameter id - The tmdbId property relating to the director.

Click to reveal the completed getForDirector() method
js
src/services/movie.service.js
async getForDirector(id, sort = 'title', order = 'ASC', limit = 6, skip = 0, userId = undefined) {
  // Get Movies directed by a Person
  // MATCH (:Person {tmdbId: $id})-[:DIRECTED]->(m:Movie)

  // Open a new session
  const session = this.driver.session()

  // Execute a query in a new Read Transaction
  const res = await session.executeRead(async tx => {
    // Get an array of IDs for the User's favorite movies
    const favorites = await this.getUserFavorites(tx, userId)

    // Retrieve a list of movies with the
    // favorite flag appened to the movie's properties
    return tx.run(`
      MATCH (:Person {tmdbId: $id})-[:DIRECTED]->(m:Movie)
      WHERE m.\`${sort}\` IS NOT NULL
      RETURN m {
        .*,
        favorite: m.tmdbId IN $favorites
      } AS movie
      ORDER BY m.\`${sort}\` ${order}
      SKIP $skip
      LIMIT $limit
    `, { skip: int(skip), limit: int(limit), favorites, id })
  })

  // Get a list of Movies from the Result
  const movies = res.records.map(row => toNativeTypes(row.get('movie')))

  // Close the session
  await session.close()

  return movies
}

Testing

To test that this functionality has been correctly implemented, run the following code in a new terminal session:

sh
Running the test
npm run test 11

The test file is located at test/challenges/11-movie-lists.spec.js.

Are you stuck? Click here for help

If you get stuck, you can see a working solution by checking out the 11-movie-lists branch by running:

sh
Check out the 11-movie-lists branch
git checkout 11-movie-lists

You may have to commit or stash your changes before checking out this branch. You can also click here to expand the Support pane.

Verifying the Test

1. How many films has Francis Ford Copolla directed?

The final test, titled should find films directed by Francis Ford Coppola, logs out the number of results returned from the API for films directed by Francis Ford Copolla.

Enter the number in the box below and click Check Answer.

  • ✓ 16

Hint

You can also find the answer by running the following Cypher statement:

cypher
MATCH (p:Person {tmdbId: "1776"})
RETURN count { (p)-[:DIRECTED]->() }

Copy the answer without any quotes or whitespace.

Solution

The answer is 16

Lesson Summary

In this Challenge, you modified the functions in the MovieService to return lists of movies.

In the next Challenge, you will implement the findById() method.