Add on-setup

ember-resources/src/core/function-based/manager.ts

@@ -1,7 +1,12 @@
 // @ts-ignore
 import { createCache, getValue } from '@glimmer/tracking/primitives/cache';
 import { assert } from '@ember/debug';
-import { associateDestroyableChild, destroy, registerDestructor } from '@ember/destroyable';
+import {
+  associateDestroyableChild,
+  destroy,
+  isDestroyed,
+  registerDestructor,
+} from '@ember/destroyable';
 // @ts-ignore
 import { invokeHelper } from '@ember/helper';
 // @ts-ignore
@@ -113,6 +118,22 @@ class FunctionResourceManager {
           cleanup: (destroyer: Destructor) => {
             registerDestructor(currentFn, destroyer);
           },
+          setup: (setuper: () => void | Destructor) => {
+            // TODO: figure out a good option here.
+            // Potential options:
+            //  - requestAnimationFrame
+            //  - requestIdleCallback
+            //  - "after render" (runloop schedule)
+            requestAnimationFrame(() => {
+              if (isDestroyed(currentFn)) return;
+
+              let destroyer = setuper();
+
+              if (destroyer) {
+                registerDestructor(currentFn, destroyer);
+              }
+            });
+          },
         },
         use,
         owner: this.owner,

ember-resources/src/core/function-based/types.ts

@@ -53,6 +53,38 @@ export type ResourceAPI = {
      *  })
      */
     cleanup: (destroyer: Destructor) => void;
+
+    /**
+     * Co-locate setup and teardown together.
+     * This allows you to keep "management variables" out of scope
+     * for the overall resource.
+     *
+     * Example:
+     * ```js
+     * import { resource, cell } from 'ember-resources';
+     *
+     * const DateTime = resource(({ on }) => {
+     *   const now = cell(new Date())
+     *
+     *   on.setup(() => {
+     *     let interval = setInterval(() => now.current = new Date(), 1000);
+     *
+     *     // This function is the cleanup
+     *     return () => clearInterval(interval);
+     *   });
+     *
+     *   on.setup(() => {
+     *     let timeout = setTimeout(() => now.current = 0, 30_000);
+     *
+     *     return () => clearTimeout(timeout);
+     *   });
+     *
+     *   return now;
+     * });
+     * ```
+     *
+     */
+    setup: (setup: () => void | Destructor) => void;
   };
 
   /**