Lightning Web Component: how can I use Get Child Records UI API?

Question

According to documentation, Lightning Data Services is built on top of UI API. So my question is: How I do to user Get Child Records UI API?

Answer 1

It looks like the answer to this is coming to us in Spring 22 in the form of lightning/uiRelatedListApi (important to note - this will be in beta).

From the Release Notes:

This module includes new wire adapters to get records, metadata, and record count for a related list.

• getRelatedListRecords—Returns record data for a related list.
• getRelatedListInfo—Returns metadata for a related list.
• getRelatedListsInfo—Returns metadata for multiple related lists.
• getRelatedListCount—Returns the record count for a related list.

The example code they provide:

import { LightningElement, wire } from 'lwc';
import { getRelatedListRecords } from 'lightning/uiRelatedListApi';

export default class LdsGetRelatedListRecords extends LightningElement {
@wire(getRelatedListRecords, {
parentRecordId: '001RM000003UNu6YAG',
relatedListId: 'Contacts',
fields: ['Contact.Name','Contact.Id']
})
}

Keep in mind because this will be a Beta feature, it may not make it to general availability, so I wouldn't start putting it in production code in the event they axe this. Hopefully not though because this'll be a really useful feature.

EDIT: Still in beta but the documentation is now available. This is the example code included:

// wireGetRelatedListRecords.js
import { LightningElement, wire } from 'lwc';
import { getRelatedListRecords } from 'lightning/uiRelatedListApi';
export default class WireGetRelatedListRecords extends LightningElement {
    error;
    records;
    @wire(getRelatedListRecords, {
        parentRecordId: '001RM000003UNu6YAG',
        relatedListId: 'Contacts',
        fields: ['Contact.Id','Contact.Name']
    })listInfo({ error, data }) {
        if (data) {
            this.records = data.records;
            this.error = undefined;
        } else if (error) {
            this.error = error;
            this.records = undefined;
        }
    }
}

Answer 2

You should be able to do this using the getRecordUi wire adapter and specifying a childRelationships parameter:

import { LightningElement, wire } from 'lwc';
import { getRecordUi } from 'lightning/uiRecordApi';

export default class Example extends LightningElement {
  @wire(getRecordUi, { recordIds: '123', childRelationships: "Account.Opportunities" })
  myRecord;
}

Note that layoutTypes and modes are still required