Custom Node: Generate properties from selected value of earlier Node

ChrisHof · April 3, 2025, 8:05pm

I’m loading an OpenAPI specification JSON (something like this) so the user can choose a path and method in an Options UI element.
I then want to output a field/property for each of the parameters that it includes in the JSON. I’m not sure how to change the options in a Collection when the selected value of the Options element before changes. Hoping someone here can help me out.
Thanks in advance!

mdmiko · April 3, 2025, 8:29pm

I’m not sure… You want to show node settings inputs based on a dropdownlist value? I’m not an expert I can only try to give an idea:
Maybe look at some other node and go to typescript source code.

Seems google sheet node and Postgres node do something similar:

github.com/n8n-io/n8n

packages/nodes-base/nodes/Postgres/v2/methods/resourceMapping.ts

master

import type { ILoadOptionsFunctions, ResourceMapperFields, FieldType } from 'n8n-workflow';

import { configurePostgres } from '../../transport';
import type { PostgresNodeCredentials } from '../helpers/interfaces';
import { getEnumValues, getEnums, getTableSchema, uniqueColumns } from '../helpers/utils';

const fieldTypeMapping: Partial<Record<FieldType, string[]>> = {
	string: ['text', 'varchar', 'character varying', 'character', 'char'],
	number: [
		'integer',
		'smallint',
		'bigint',
		'decimal',
		'numeric',
		'real',
		'double precision',
		'smallserial',
		'serial',
		'bigserial',
	],

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github.com/n8n-io/n8n

packages/nodes-base/nodes/Google/Sheet/v2/methods/resourceMapping.ts

master

import type {
	IDataObject,
	ILoadOptionsFunctions,
	ResourceMapperField,
	ResourceMapperFields,
} from 'n8n-workflow';

import { GoogleSheet } from '../helpers/GoogleSheet';
import { ROW_NUMBER, type ResourceLocator } from '../helpers/GoogleSheets.types';
import { getSpreadsheetId } from '../helpers/GoogleSheets.utils';

export async function getMappingColumns(
	this: ILoadOptionsFunctions,
): Promise<ResourceMapperFields> {
	const documentId = this.getNodeParameter('documentId', 0) as IDataObject | null;

	if (!documentId) return { fields: [] };

	const { mode, value } = documentId;

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ChrisHof · April 4, 2025, 9:21am

Thanks, those two got me going in the right direction!

system · April 11, 2025, 9:22am

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