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Using Aliases to Rename Fields

3:37 with Isaac Lee Morris

Fields can overlap when you are querying the same field with different arguments. In this video we will discuss the syntax for aliasing a field and show a query with the same field aliased twice.

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Course repo: Use this GitHub repo to follow along with this video in the course

(Apollo's Launchpad has been deprecated, so your screen will look different)

New Terms:

Fragment - Reusable sets of fields that can be included in multiple queries; saves time from needing to manually include the same fields over and over in many places

Further Reading:

GraphQL Fragments are the Best Match for UI Components by Samer Buna

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Up until this point, when we want to include a field in our response, 0:00

we specify each field individually. 0:05

Now this is fine for experimenting, but when building an actual project, 0:08

there's a good chance we'll need to grab the same fields in multiple places. 0:13

Fortunately GraphQL makes this possible with a concept called fragments. 0:18

A fragment is simply a block of code 0:24

that specifies a group of fields that you want to include in your response. 0:27

To see how this works let's jump back in the Launchpad for an example. 0:32

For this example, we'll be using the movie by ID in point again, 0:36

aliased under movieOne and movieTwo. 0:41

Just like in the last video, we'll start with our query declaration. 0:44

Then we'll go ahead and write the first call the movieById, 0:49

which will be aliased under movieOne. 0:53

For this one, we'll use the movieId of movie_0, 0:58

then in our response we'll include the id, 1:04

title, tagline, and revenue fields. 1:09

Now let's go ahead and repeat the same thing for movieTwo. 1:14

Again, we've got the alias of movieTwo calling movieById. 1:18

The movieId we'll use for this one is movie_1. 1:25

And we'll go ahead and include those same fields again, 1:32

id, title, tagline and revenue. 1:37

Right now when we want to include the same fields for 1:41

each movie, we have to manually type those fields out inside of each end point call. 1:43

Now go ahead and run the query. 1:50

As expected it works fine, we have both of our movies, but 1:55

it was a little repetitive to type it all out. 1:58

You can probably see how this could get tedious pretty quickly. 2:02

This is exactly where fragments come in handy. 2:06

To define a new fragment we'll start with the fragment key word. 2:09

This fragment we'll call movie details. 2:14

We then need to tell GraphQL which type this fragment can be used on 2:20

using the on keyword followed by the Movie type. 2:25

After that, it's just like any other query. 2:31

Inside of the curly brackets we'll go ahead and 2:33

copy paste the fields we used from our query above. 2:37

Now let's modify those queries a bit. 2:52

Inside of the curly brackets, go ahead and delete those fields. 2:55

Now, instead of typing them all out, we can just include our new fragment. 3:04

To do this type in three dots followed by the fragment name, 3:09

which in this case is movieDetails. 3:13

I did the same thing for movieTwo. 3:19

Now go ahead and run that query. 3:24

As you can see, it works like a charm. 3:27

Using fragments when we need to retrieve the same information 3:30

can save us quite a bit of time and quite a bit of typing. 3:33

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