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Introduction to GraphQL

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Selecting Fields

3:05 with Isaac Lee Morris

In this video, we will go over how to fetch data in the shape we want it, including only the pieces that we care about.

Course Repo: Use this GitHub Repo to follow along with this course

New Terms:

  • Scalar field - A field with a simple data type, such as a String, Int, or Boolean
  • Object type field - A field which returns another object, which can be broken down into further scalar or object type fields

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    Now that we're familiar with all the pieces, 0:00
    let's bring it all together into a query. 0:02
    In this video, we'll try adding and 0:05
    removing fields to see how that affects our query results. 0:07
    Once again, we'll be working with movie objects. 0:12
    You can find the link to the starting point for 0:15
    this lesson in the Teacher's Notes under Stage 2- Video 2. 0:17
    As we saw in the previous stage, each movie has five fields, 0:22
    id, title, tagline, revenue and studio. 0:26
    With the exception of studio, each of these is what's known as a scalar field. 0:32
    This means they are simple fields like strings and 0:38
    numbers that can't be broken down into more nested objects. 0:41
    Let's start by writing a small query that selects a single scalar field id. 0:45
    As we saw in the last video, we'll start with the query 0:51
    declaration followed by the topMovieByRevenue endpoint name, 0:56
    followed by the field we want to select, id. 1:02
    Go ahead and click Play. 1:06
    And there we see we've got the movie with the highest box office 1:10
    revenue with only its id. 1:13
    So what would happen if we ask GraphQL for 1:16
    a field that doesn't exist on the movie object? 1:18
    Let's try it. 1:21
    After Id, add a poster field. 1:25
    Go ahead and run the query. 1:29
    As you can see, 1:33
    GraphiQL's thrown an error, Cannot query field poster on type movie. 1:34
    This is because movie objects don't contain a corresponding poster field. 1:39
    Now that we’ve gone over scaler fields, let me introduce you to another type. 1:46
    The object type field. 1:51
    These fields are the meat of what really makes GraphiQL such a pleasure to use. 1:54
    An object type field is a field the returns another object, 1:59
    which means we can also specify which fields we want to return from that object. 2:03
    Let's try it out. 2:09
    First, remove the invalid poster field from earlier so 2:10
    that we don't get an error. 2:14
    And we'll go ahead and replace it with a studio field. 2:17
    This will return an object of the studio type, which has two fields, name and 2:22
    location. 2:27
    Since this is an object type field, 2:28
    we'll add some curly braces after the field name. 2:30
    And then we'll specify which subfields we want returned inside of them. 2:35
    For now, just enter the name field. 2:39
    If this seems familiar, that's because it is. 2:43
    Object type fields are queried just like endpoints. 2:46
    You have some curly braces containing a list of the fields that we want returned. 2:49
    Go ahead and run the updated query. 2:54
    There you have it! 2:59
    Inside of our movie object, 3:00
    we can see the name of the studio where our movie was created. 3:01

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