📥 Retrieving our data
Our schema is freshly updated with new types and a new query for fetching a given track. We'll need to implement resolvers and data source methods for these new fields.
Our REST API can be found here: https://odyssey-lift-off-rest-api.herokuapp.com.
It has a GET track/:id
endpoint, which takes the track ID as a parameter and returns that track's data. Let's first try out this endpoint: give it a track ID c_0
and check if it provides us with all the necessary data.
Here's the full GET /track/c_0
response:
{"id": "c_0","thumbnail": "https://res.cloudinary.com/dety84pbu/image/upload/v1598465568/nebula_cat_djkt9r.jpg","topic": "Cat-stronomy","authorId": "cat-1","title": "Cat-stronomy, an introduction","description": "Curious to learn what Cat-stronomy is all about? Explore the planetary and celestial alignments and how they have affected our space missions.","numberOfViews": 0,"createdAt": "2018-09-10T07:13:53.020Z","length": 2377,"modulesCount": 10,"modules": ["l_0","l_1","l_2","l_3","l_4","l_5","l_6","l_7","l_8","l_9"]}
Looking closely at the shape of that response, we can see that we do get the description
and the numberOfViews
. That's great! We also get an array of modules, but they're only IDs, and we'll need more details than that. We'll have to use another endpoint to get those details later.
c_1
. What's the first module ID on the list?💾 Updating the RESTDataSource
Let's take care of our TrackAPI
, the data source in charge of calling our REST API and retrieving the data. We can find it in the server/src/datasources
folder, in the track-api.js
file.
Let's create a new method to get a single track based on its ID. Let's call it getTrack
, and it'll take a trackId
as a parameter.
We'll use the get
method provided by our RESTDataSource
class to make a call to the track/:id
endpoint, passing it the trackId
from the arguments. Then, we'll return the results.
In track-api.js
, add the following method to the TrackAPI
class:
getTrack(trackId) {return this.get(`track/${trackId}`);}
Now that our data source is retrieving the data, our resolver should be able to use it! In Lift-off II, we already worked out the connection between our resolvers and data sources inside the ApolloServer
configuration options, so we should be good to add more resolvers as necessary.
✍️ Adding a new resolver
Let's take care of this track
resolver. In the server/src
folder, open up the resolvers.js
file.
In our Query
object, we'll add a new function below tracksForHome
. In our schema, we named the fieldtrack
, so here it has to have the same name.
Recall that a resolver is a function with four optional parameters: parent
, args
, context
, and info
.
In resolvers.js
, add the following after the tracksForHome
resolver:
track: (parent, args, context, info) => {},
We've used the third argument context
before, to access the dataSources
key. This is where our trackAPI.getTrack
method lives. This method expects the id
of a track. We'll specify that value later as an argument when we build the query.
To access this id
, we can use the second parameter in the resolver: args
. args
is an object that contains all GraphQL arguments that were provided for the field. We can destructure this object to access the id
property, then pass that id
into our getTrack
method.
Then, we can return the results of that method.
Update the track
resolver in resolvers.js
:
track: (parent, {id}, {dataSources}, info) => {return dataSources.trackAPI.getTrack(id);},
Finally, let's clean up our two other parameters. We can replace parent
with an underscore since we won't be using it, and we can omit the last parameter info
altogether; we won't use it either.
Let's not forget to add a nice little comment above to help teammates and future you make sense of what this resolver does.
Update the track
resolver in resolvers.js
:
// get a single track by ID, for the track pagetrack: (_, {id}, {dataSources}) => {return dataSources.trackAPI.getTrack(id);},
Write a resolver function for the spaceCat
field to query a spaceCat by ID. Follow the conventions used above for the four resolver parameters, and use arrow function syntax.. Use the dataSources
object to access the spaceCatsAPI.getSpaceCat()
method, which takes the id
from args
and returns the results.
We're done with our track resolver, but not quite finished with our resolver work yet. If you recall, the track data returned by our REST API has a modules
property, but it only contains a list of module IDs. Next, we'll need to make sure we're getting the details of each module.
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