Specifying Default Variables

In our final video I'm gonna show you one last trick 0:00 to make your GraphQL more reusable. 0:04 In the last lesson you learned how to extract 0:07 arguments into variables that could be passed in with a variables object. 0:10 But what about when you've only got some of the arguments you need? 0:14 GraphQL helps out here as well, with a feature called default variables. 0:18 Let's hop on over to Launchpad and check it out. 0:23 In this example, we'll be calling a new endpoint, random movie by year. 0:26 This endpoint doesn't take a movie ID, like the movie by ID endpoint, 0:32 instead this movie takes an integer named year. 0:37 And returns a random movie that was released that year. 0:40 Before we write the query go ahead and take a peak at the schema. 0:44 First you'll see that we've added another field to the movie type. 0:49 This new field is called releaseYear and has a type of Int for integer. 0:53 Like I mentioned before, 1:00 the randomMovieByYear endpoint takes just a single argument with a type of Int. 1:02 Which is required and returns a Movie object. 1:07 Back to writing our query. 1:10 This query is gonna look very similar to the query from the last video. 1:12 We'll start with the declaration, Followed by declaring the variable, 1:17 which will be named $year, and we'll have a type of Int. 1:24 Inside the curly brackets for our query we'll call the randomMovieByYear 1:32 endpoint using that $year variable for the year argument. 1:37 In our response, let's return the movie Iid the title, and the releaseYear. 1:45 Going back to our variable declaration, 1:53 you might have noticed that we didn't require the year variable this time. 1:55 So, what happens if we run this query without passing in any variable values? 1:59 Go ahead and click the play button, and there you'll see GraphiQL throws an error. 2:04 This is because, even though our query doesn't require the year, 2:10 the randomMovieByYear, endpoint inside of it does. 2:14 So, if our query isn't given the variable it needs, 2:18 we need to specify a default value to be used. 2:21 This is where default variables come in. 2:25 To define a default variable after the variable 2:28 type add an = followed by the value. 2:33 In this case we'll say 2000, now run the query again. 2:37 There we go, we've got one movie. 2:46 If we click it again, we get another movie. 2:49 What if we want to pass in a variable using our query variables pane? 2:52 Well, let's go ahead and try doing that. 2:56 I'll go ahead and pass in a variable for year, this time we'll use 2001. 3:02 Go ahead and run that query. 3:08 And there we go, we've got a movie from 2001. 3:11 As you can see, since we specified a variable value, GraphiQL used that one 3:14 instead of the default, and returned a random movie from 2001. 3:19 So that wraps up our introduction to GraphQL, 3:25 I encourage you to keep playing around in Launchpad. 3:28 Try defining some of your own queries, mutations, and fragments. 3:31 As always, don't forget to check out the teacher's notes for 3:35 helpful resources on GraphQL, see you. 3:38