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Version: v2.x

Creating Actions

Introduction

An action is a GraphQL query or mutation. You have to define the GraphQL type of the arguments that the query or mutation accepts and the GraphQL type of its response.

To create an action, you have to:

  1. Define the query or mutation
  2. Define the required types
  3. Create a handler

Let's look at examples for mutation and query type actions.

Setup

There is no setup required for defining actions via the console.

Mutation type action

Let's start with a mutation that accepts a username and password, and returns an access token. We'll call this mutation login.

Step 1: Define your mutation and associated types

Start with defining the mutation and the required types. These types will reflect in the GraphQL schema.

Go to the Actions tab on the console and click on Create. This will take you to a page like this:

Console action create

Define the action as follows in the Action Definition editor.

type Mutation {
login (username: String!, password: String!): LoginResponse
}

In the above action, we called the returning object type to be LoginResponse. Define it in the New types definition as:

type LoginResponse {
accessToken: String!
}

The above definition means:

  • This action will be available in your GraphQL schema as a mutation called login.
  • It accepts two arguments called username and password of type String!.
  • It returns an output type called LoginResponse.
  • LoginResponse is a simple object type with a field called accessToken of type String!.

Step 2: Create the action handler

A handler is an HTTP webhook where you can perform the custom logic for the action.

In this case, we will just return an access token, but typically you would want to run all the business logic that the action demands. NodeJS/Express code for this handler would look something like:

const handler = (req, resp) => {
// You can access their arguments input at req.body.input
const { username, password } = req.body.input;

// perform your custom business logic
// check if the username and password are valid and login the user

// return the response
return resp.json({
accessToken: "Ew8jkGCNDGAo7p35RV72e0Lk3RGJoJKB"
})

};

You can deploy this code somewhere and get the URI. For getting started quickly, we also have this handler ready at https://hasura-actions-demo.glitch.me/login.

Set the handler

Now, set the handler for the action:

Set the value of the handler field to the above endpoint.


URL templating

To manage handler endpoints across environments it is possible to template the endpoints using ENV variables.

e.g. https://my-handler-endpoint/addNumbers can be templated to {{ACTION_BASE_ENDPOINT}}/addNumbers where ACTION_BASE_ENDPOINT is an ENV variable whose value is set to https://my-handler-endpoint

Note

If you are running Hasura using Docker, ensure that the Hasura Docker container can reach the handler endpoint. See this page for Docker networking.

Step 3: Finish action creation

Finally, to save the action:

Hit Create.

Step 4: Try it out

In the Hasura console, head to the GraphiQL tab and try out the new action.

GraphiQL
Query Variables
Request Headers

And that's it. You have extended your Hasura schema with a new mutation.

Query type action

Let's start with a basic query that accepts a list of numbers and returns their sum. We'll call this query addNumbers.

Step 1: Define your query and associated types

Start with defining the query and the required types. These types will reflect in the GraphQL schema.

Go to the Actions tab on the console and click on Create. This will take you to a page like this:

Console action create

Define the action as follows in the Action Definition editor.

type Query {
addNumbers (numbers: [Int]): AddResult
}

In the above action, we called the returning object type to be AddResult. Define it in the New types definition as:

type AddResult {
sum: Int
}

The above definition means:

  • This action will be available in your GraphQL schema as a query called addNumbers
  • It accepts an argument called numbers which is a list of integers.
  • It returns an output type called AddResult.
  • AddResult is a simple object type with a field called sum of type integer.

Step 2: Create the action handler

A handler is an HTTP webhook where you can perform the custom logic for the action.

In this case, it is the addition of the numbers. NodeJS/Express code for this handler would look something like:

const handler = (req, resp) => {
// You can access their arguments input at req.body.input
const { numbers } = req.body.input;

// perform your custom business logic
// return an error or response
try {
return resp.json({
sum: numbers.reduce((s, n) => s + n, 0)
});
} catch(e) {
console.error(e)
return resp.status(500).json({
message: 'unexpected'
})
}
};

You can deploy this code somewhere and get the URI. For getting started quickly, we also have this handler ready at https://hasura-actions-demo.glitch.me/addNumbers.

Set the handler

Now, set the handler for the action:

Set the value of the handler field to the above endpoint.

URL templating

To manage handler endpoints across environments it is possible to template the endpoints using ENV variables.

e.g. https://my-handler-endpoint/addNumbers can be templated to {{ACTION_BASE_ENDPOINT}}/addNumbers where ACTION_BASE_ENDPOINT is an ENV variable whose value is set to https://my-handler-endpoint

Step 3: Finish action creation

Finally, to save the action:

Hit Create.

Step 4: Try it out

In the Hasura console, head to the GraphiQL tab and try out the new action.

GraphiQL
Query Variables
Request Headers

And that's it. You have extended your Hasura schema with a new query.

Additional Resources

Introduction to Hasura Actions - View Recording.