Add readme for extensions

README.md

@@ -51,6 +51,34 @@ const directus = createDirectus<Collections>(
 })();
 ```
 
+### Usage in Directus extensions
+
+```typescript
+import {defineEndpoint} from '@directus/extensions-sdk';
+import type {CollectionName} from "../models";
+import type {ItemsService} from "@directus/api/dist/services";
+import {ItemIn} from "directus-app/models";
+
+export default defineEndpoint((router, {services}) => {
+    /**
+     * You probably want to move this utility to a place more suitable
+     * for your extension
+     */
+    function items<C extends CollectionName>(collectionName: C): ItemsService<ItemIn<C>> {
+        return new services.ItemsService(collectionName);
+    }
+
+    router.get('/', async (_req, res) => {
+        const settings = await items('directus_settings')
+            .readSingleton({});
+
+        res.json({
+            name: settings.project_name
+        });
+    });
+});
+```
+
 ## Note: Geometry Support
 
 I am still working on support for the geometry types.

src/index.ts

@@ -196,10 +196,14 @@ export default defineHook(async ({init}, {services, getSchema, database, logger}
                 source += generateIndex(collections);
 
                 source += `
-type ItemType<CollectionKey extends keyof Collections> =
+
+type CollectionName = keyof Collections;
+
+type ItemIn<CollectionKey extends CollectionName> =
     Collections[CollectionKey] extends (infer Item)[]
-        ? Item
-        : Collections[CollectionKey];
+        ? Exclude<Item, unknown>
+        : Collections[CollectionKey]
+
 `
                 await writeFile(file, source);
                 process.exit(0);