useMutation hook in GraphQL - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of the useMutation hook in GraphQL?

The useMutation hook is used to send data-changing requests (mutations) to a GraphQL server, such as creating, updating, or deleting data.

beginner

How do you call a mutation function returned by useMutation?

You call the mutation function like a regular function, optionally passing variables as an object, for example: mutateFunction({ variables: { id: 1 } }).

intermediate

What does useMutation return?

useMutation returns an array with two elements: the mutation function to trigger the mutation, and an object containing the mutation's current status like loading, error, and data.

intermediate

Why is it important to handle the loading and error states when using useMutation?

Handling loading shows the user the mutation is in progress, and handling error helps display any problems that happened during the mutation, improving user experience.

advanced

Can you update the UI automatically after a mutation using useMutation? How?

Yes, you can update the UI by using the refetchQueries option to reload queries or by updating the Apollo cache manually in the update callback after the mutation completes.

What does the useMutation hook primarily do?

A Send data-changing requests to the server

B Fetch data from the server

C Subscribe to real-time data updates

D Manage local component state

The useMutation hook is designed to send mutations, which change data on the server.

What is the first element returned by useMutation?

A An object with loading and error states

B A function to trigger the mutation

C The mutation result data

D A boolean indicating success

The first element is the mutation function you call to execute the mutation.

How do you pass variables to a mutation using useMutation?

A Variables are not supported in mutations

B By setting a global variable before calling the mutation

C By including variables in the GraphQL query string

D Inside the mutation function call as an object with a <code>variables</code> key

Variables are passed as an object inside the mutation function call under the variables key.

Which of these is NOT part of the mutation result object returned by useMutation?

A <code>subscribe</code>

B <code>error</code>

C <code>data</code>

D <code>loading</code>

subscribe is not part of the mutation result; it relates to subscriptions.

What option can you use with useMutation to automatically refresh queries after a mutation?

A <code>variables</code>

B <code>onCompleted</code>

C <code>refetchQueries</code>

D <code>fetchPolicy</code>

refetchQueries lets you specify queries to reload after the mutation finishes.

Explain how to use the useMutation hook to send a mutation and handle its result.

Think about the steps from setup to calling and handling the mutation.

Describe ways to update the UI after a mutation using useMutation.

Consider how to keep the UI in sync with server changes.