Medplum

# FHIR Operations This folder contains implementations of [FHIR Operations](https://hl7.org/fhir/operations.html) See [this list of defined operations](https://hl7.org/fhir/operationslist.html) ## Implementing an Operation All Operations supported by the server should have a corresponding [`OperationDefinition`][op-def] resource that specifies important details including: - Typed input and output parameters - Which REST routes the Operation is available on - If the Operation is idempotent Utility functions that use the `OperationDefinition` to automate implementation details are available: - [`parseInputParameters`](./utils/parameters.ts) takes either standard `Parameters` input or plain JSON key-value pairs for compatibility, and produces an object containing all defined input parameter values - Validates number of parameter values, including required parameters - [`buildOutputParameters`](./utils/parameters.ts) handles sending a set of output values as the response - Only sends parameters defined in the `OperationDefinition` - Validates parameter cardinality and throws a server error when response wouldn't match `OperationDefinition` - Can be passed a `Resource` when there is one matching output parameter named `return` ### Example: Project $init ```ts import { buildOutputParameters, parseInputParameters } from './utils/parameters'; import { created } from '@medplum/core'; import { Reference, OperationDefinition } from '@medplum/fhirtypes'; import { Request, Response } from 'express'; const operation: OperationDefinition = { resourceType: 'OperationDefinition', name: 'project-init', status: 'active', kind: 'operation', code: 'init', resource: ['Project'], system: false, type: true, // Available at route /Project/$init only instance: false, parameter: [ // Required param: name (string) { use: 'in', name: 'name', type: 'string', min: 1, max: '1' }, // Optional params: owner (Reference), ownerEmail (string) { use: 'in', name: 'owner', type: 'Reference', min: 0, max: '1' }, { use: 'in', name: 'ownerEmail', type: 'string', min: 0, max: '1' }, // Output parameter: Project { use: 'out', name: 'return', type: 'Project', min: 1, max: '1' }, ], }; interface ProjectInitParameters { name: string; owner?: Reference; ownerEmail?: string; } export async function projectInitHandler(req: FhirRequest): Promise<FhirResponse> { const params = parseInputParameters<ProjectInitParameters>(operation, req); // Handle operation business logic... const project = doProjectInit(params); // Special case: single `return` output parameter means respond with the Project resource directly return [created, project]; } ```