Services
In ElectroDB a Service
represents a collection of related Entities. Services allow you to build queries that span across Entities. Similar to Entities, Services can coexist on a single table without collision. You can use Entities independent of Services, you do not need to import models into a Service to use them individually; However, you do need to use a Service if you intend to make queries that “join” multiple Entities.
Creation
The property name you assign the entity will then be “alias”, or name, you can reference that entity by through the Service. Aliases can be useful if you are building a service with multiple versions of the same entity or wish to change the reference name of an entity without impacting the schema/key names of that entity.
import { Service } from "electrodb";
const TaskApp = new Service(
{
employee: Employee, // available at TaskApp.entities.personnel
task: Task, // available at TaskApp.entities.directives
},
{ table, client },
);
Services take an optional second parameter, similar to Entities, with a client
and table
. Using this constructor interface, the Service will utilize the values from those entities, if they were provided, or be passed values to override the client
or table
name on the individual entities.
Options
Property | Description |
---|---|
table | The name of the dynamodb table in aws. |
client | (optional) An instance of the docClient from the aws-sdk for use when querying a DynamoDB table. This is optional if you wish to only use the params functionality, but required if you actually need to query against a database. |
Validation
When joining an Entity to a Service, ElectroDB will perform numerous validations to ensure the provided Entities are consistently defined. The following is a list of the validations performed on Service creation:
- Entity names must be unique across a Service.
- Collection names must be unique across a Service.
- All Collections map to the same DynamoDB indexes with the same index field names. See Indexes.
- Partition Key [Composite Attributes](#composite attribute-arrays) on a Collection must have the same attribute names and labels (if applicable). See Attribute Definitions.
- The name of the Service in the Model must match the Name defined on the Service instance.
- If the attributes of an Entity have overlapping names with other attributes in that service, they must all have compatible or matching attribute definitions.