Comment on page


When relationships are defined during the customization step, Forest Admin Collections act as if the 2 Collections were natively linked at the data source level.
You may have noticed that relationships within a data source are configured out of the box, so you won't need to define those.
However, you may want to create additional intra and cross data source relationships to:
  • help users navigate within your admin panel,
  • create charts that use data from multiple data sources,
  • let users filter, use scopes, or segment with conditions that cross data source boundaries.

Minimal example

agent.customizeCollection('towns', collection =>
// Towns belong to 1 country
.addManyToOneRelation('country', 'countries', { foreignKey: 'country_id' })
// Towns have 1 mayor
.addOneToOneRelation('mayor', 'mayors', { originKey: 'town_id' })
// Towns have multiple inhabitants
.addOneToManyRelation('inhabitants', 'people', { originKey: 'town_id' })
// Towns electricity is supplied by power plants that are shared with other towns
.addManyToManyRelation('energyProviders', 'powerPlants', 'utilityContracts', {
originKey: 'town_id',
foreignKey: 'power_plant_id',
// Towns have a list of honorary citizen that is retrievable through a public API
.addExternalRelation('honoraryCitizen', {
schema: { firstName: 'String', lastName: 'String' },
listRecords: async ({ id }) => {
const response = await axios.get(
return response.body;