Change Data with GraphQL Mutations

Instructor: [00:00] Let's create a variable called skiDays that we'll set to . Then we'll adjust our totalDays resolve to return skiDays. Next, in our schema we'll create a mutation type, and the two mutations I want to create are addDay which should return an int, and removeDay which should also return an int. Then we'll adjust the resolvers. We'll add a mutation object with two functions, one to increment or add a day, and one to decrement or remove a day.

[00:34] Now in the playground we can test the query and the mutations. First let's query totalDays. Then we want to test addDay. You'll notice that when I add this, we have a red underline. You're only allowed to have one anonymous operation in a query document, so I'll need to give each of these an operation name. Then I can execute the mutation by clicking play and choosing the operation name from the dropdown.

[01:02] Finally, let's test the removeDay mutation and we'll see that it is indeed removing days from our total. To recap, mutations are a type defined in the schema and mutations have resolver functions that match the names in that schema.