Creating relationships

This chapter assumes that that the reader has the code that was created in the previous tutorials:

1. Creating a new project
2. Adding lists

To-single relationship

Let's link the Todo list and the User list together by setting up a relationship. Tweak the assignee field in Todo.js to match the following code:

Import the Relationship field:

const { CalendarDay, Checkbox, Relationship, Text } = require('@keystonejs/fields');

Update the field type from Text to Relationship and provide a ref that points to which list the field is related to.

assignee: {
-  type: Text,
+  type: Relationship,
+  ref: 'User',
  isRequired: true,
}

The ref option defines the List to which we will relate. The name assigned to the option is the same name that is passed to createList. In the Admin UI you can now pick one of the created users to make them responsible for completing the task.

Two-way to-single relationship

It is now possible to assign a task to a user, but it is not possible to assign the user to a task! In User.js add the following field:

task: {
  type: Relationship,
  ref: 'Todo',
}

Now we can set a task for the User from the admin panel. But something is wrong! When we pick a task for the user and then check this task, the assignee is incorrect. This is because we have create two separate one-sided relationships. What we want is a single two-sided relationship.

Setting up a two-sided relationship between User and Todo

In order to indicate that task and assignee are just two different sides of a single relationship, we need to update our configurations In User.js adjust the task field to the following:

task: {
  type: Relationship,
-  ref: 'Todo',
+  ref: 'Todo.assignee',
}

And in Todo.js update the assignee field:

assignee: {
  type: Relationship,
-  ref: 'User',
+  ref: 'User.task',
}

Start the Admin UI, create a Todo and assign a user. Check the user's task field and notice that it is already set!

To-many relationship

What if a user needs to be able to do multiple tasks? Keystone provides a way to do this easily. Take a look at following code in User.js:

tasks: {
  type: Relationship,
  ref: 'Todo.assignee',
  many: true,
}

The many: true option indicates that User can store multiple references to tasks.

Note: we've updated the name of the field from task to tasks to indicate the nature of the relationship.

Copy this code to your application and don't forget to change the assignee field in Todo.js to match the new field name User.tasks. Now in the Admin UI you can pick multiple tasks for a user.

See also:

• Relationships
• Schema - Lists & Fields
• Field Types - Relationship